Posterior cruciate ligament tibial inlay reconstruction

Posterior Cruciate Ligament Tibia1 Inlay Reconstruction EugeneE. Berg, M.D.

Summary: A patellar bone-tendon-bone tibia1 inlay reconstruction of the posterior cmciate ligament using a popliteal arthrotomy was designed to minimize grafttunnel wall abrasion. Arthroscopic techniques are used for femoral graft fixation. In a small series, the procedure decreased the quadriceps active drawer in 70” of flexion by an average of 4 mm and improved patellofemoral symptoms. Key Words: Posterior cruciate ligament-Posterior cruciate reconstruction-Popliteal approach-Patellar tendon graft.

T

he posterior cruciate ligament (PCL) is injured infrequently, with an incidence estimated between 3% and 16% of all injuries to the knee.‘” There is less information and literature on posterior cruciate anatomy, mechanics, and function than that of its kindred anterior cruciate ligament (ACL). Thus, many of the principles of PCL surgery have been borrowed from reconstructive successes with the more commonly injured ACL. Unlike the ACL, the tibia1 insertion of the PCL is extrasynovial. Yet most PCL reconstructions use an anterior approach with limited popliteal fossa exposure.‘,2,4-8 This creates a long oblique interosseous tibia1 tunnel that makes passage of the ligament substitute technically difficult, especially with a patellar bone-tendon-bone graft. In a 1992 American Academy of Orthopaedic Surgeons Instructional Course lecture, one panelist (Marc Friedman) called this “the killer turn”. It is of theoretical concern that this sharp angle at the proximal tibia1 tunnel margin may act as an abrasive ridge that could cause ligament graft failure. Friction between the extensive tibia1 tunnel wall and the ligament substitute, as well as the acute bend of the graft at the tunnel exit may cause ineffective in situ graft pretensioning.

From the Department of Orthopaedics, the University of South Carolina School of Medicine, Columbia, South Carolina, U.S.A. Address correspondence and reprint requests to Eugene E. Berg, M.D., Two Richland Medical Park, Suite 404, Columbia, SC 29203, U.S.A. 0 1995 by the Arthroscopy Association of North America 0749-8063/95/l 101.1087$3.00/0

Arthroscopy:

The Journal

of Arthroscopic

Repairs of sutured intrasubstance ligament tears have yielded inconsistent and disappointing clinical results.’ Therefore, reconstructive efforts have emphasized the selection of ligament graft substitutes with supraphysiological tensile strengths.‘X2,9 Perhaps the emphasis on the tensile material properties of cruciate ligament substitutes has been over emphasized. There is increasing evidence that ligament failure does not always result from distractive tensile loads. Several studies have shown, with strong statistical correlation, that bilateral, noncontact ACL injuries occur in patients with stenotic intercondylar notches.“-” Thus, ACL tears may occur in a three-point bend mode as the collagenous ligament interstitium is amputated by an osteophytic intercondylar notch in hyperextension or internal rotation.“-” Abrasion at the bone-tunnel margin has also been identified as a major cause of synthetic ligament failure even when the synthetic material has superior tensile properties.‘3-‘6 The following procedure with popliteal fossa exposure and secure patellar tendon-bone block inlay fixation on the tibia, was devised to circumvent the technical problems of PCL reconstructions from an anterior surgical approach, which by necessity must create a long oblique tibia1 tunnel.

SURGICAL

TECHNIQUE

If the patellar tendon is long, the bony portion of the tendon graft will be recessed proximally within the femoral tunnel, which may subject the tendon to

and Related Surgery,

Vol II, No 1 (February),

1995: pp 69-76

69

70

E. E. BERG

FIG 1. PCL size is determined on a calibrated 30” to 70” flexed lateral knee radiograph. In this cadavetic specimen, the PCL origin and insertion were painted with a radio-opaque tantalum preparation. PCL length is measured from the anterior margin of the intercondylar line to 1 cm below the tibia1 joint surface. Patellar tendon length is measured from the posterior surface from the tibia1 tuberosity to thy inferior patellar pole. If the native patellar tendon is more than 1~ cm longer than the PCL. An allograft of measured soft tissue length is preferred to prevent graft recession in the femoral tunnel.

abrasive attenuation. Therefore, the autogenous patellar tendon is sized on a calibrated, 30” flexed, lateral knee radiograph with 3 mm or less of perfect posterior femoral condylar overlap (Fig 1). A high-intensity illuminator will discern the exact tibia1 tuberosity insertion site of the patellar tendon, just anterior to the fat pad density. PCL length is measured from the anterior margin of the intercondylar line to a point 1 cm below the posterior tibia. If the autogenous patellar tendon is greater than the measured PCL length by more than 1; cm, the surgeon should consider use of an allograft of specified tendon length. (In this series, the combined ACL/PCL reconstructions had ACL patellar tendon autografts and PCL allografts. Contralateral autografts were not procured to avoid good leg morbidity.) The patient is placed in a decubitus position with the operative leg on the upside. The limb is circumferentially prepped and draped from proximal thigh to mid calf. The hip is abducted and externally rotated 45”; with the knee flexed 90”, the anterior knee faces

the arthroscopist (Fig 2). A l-cm wide, central third patellar bone-tendon-bone autograft is obtained. The tibial tubercle bone block is drilled and tapped to accept a 6.5 cancellous screw and spiked washer. Standard anterior arthroscopic portals are used to examine intraarticular structures and perform meniscal surgery as needed. Via the anteromedial portal, a femoral jig is placed in the anterior superior femoral origin of the PCL, 4 mm from the articular margin of the medial femoral condyle (Fig 3). A 5-cm incision is made proximal to the medial femoral epicondyle. The patellar retinaculum is divided and the condyle exposed subperiosteally. After guide-pin placement, a cannulated reamer is used to create a l-cm diameter interosseous tunnel in the medial femoral condyle. The tunnel margins are chamfered with rasps. An 18 gauge wire loop is passed through the femoral tunnel, directed towards the posterior joint, and will be used to pass the patellar tendon graft retrograde into the femoral tunnel later in the case. Because the popliteal arthrotomy will cause extravasation of the arthroscopic irrigant, in combined ACL/PCL procedures, the ACL reconstruction is performed first. The knee is extended, the table tilted towards a prone position, and the thigh is abducted using stacked towels to permit access to the popliteal fossa (Fig 4A). A vertical incision is fashioned in line with the palpable semitendinosus tendon. The incision veers laterally in the popliteal crease and extends distally over the posterior calf (Fig 4). The deep fascia overlying the gastrocnemius muscle is exposed and incised vertically. The sural

FIG 2. In the decubitus position with the thigh abducted and knee and hip flexed, the anterior knee is accessible to standard arthroscopic portals and surgical techniques.

PCL TIBIAL INLAY RECONSTRUCTION

FIG 3. The drill guide is placed in the anterior superior femoral origin of the PCL, 4 mm from the articular margin of the medial femoral condyle.

FIG 4. Position 2: the hip and knee are extended, the table is tilted towards a prone position, and the leg is abducted by stacked towels. The popliteal fossa is now surgically accessible. (Inset) A vertical incision is fashioned in line with the palpable semitendinosus tendon. It veers laterally in the popliteal crease and extends distally over the calf.

POSITION

71

nerve is visualized between the two heads of gastrocnemius muscle and is protected. The plane between the medial head of the gastrocnemius and the semimembranosus tendon is identified and developed bluntly. A slight amount of knee flexion will facilitate the exposure and allow relief of tension on the popliteal vessels (Fig 5). The medial head gastrocnemius tendon is incised near its insertion and is retracted laterally, protecting its tibia1 nerve motor branch (Fig 6). The inferior medial geniculate artery and vein are identified overlying the posterior joint capsule at the superior margin of the popliteus muscle and are ligated (Fig 6). A vertical incision is made through the oblique popliteal ligament and posterior capsule. The insertion of the posterior cruciate ligament is visualized and the posterior tibia1 plateau exposed subperiosteally (Fig 6B inset). The tendon graft traction sutures are advanced with the wire loop retrograde into the medial femoral condyle tunnel. A 7- or 9-mm diameter cannulated screw is used to secure interference fixation of the bone graft in the femoral tunnel. Optimally, the bone portion of the graft should not be recessed within the condylar tunnel but should lie at the tunnel-margin interface to prevent tendon-tunnel wall abrasion. Avoiding recurvatum, the knee is positioned in full extension, which reduces posterior tibia1 subluxation

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E. E. BERG

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FIG 5. The deep fascia overlying the gastrocnemius muscle incised, the sural nerve is visualized and protected. The knee flexed slightly to relieve pressure on the popliteal vessels.

is is

via the geometric congruity of the femoral condyle and tibia1 plateau. The patellar tendon graft is placed under slight manual tension, which determines the site of posterior tibia1 fixation. An osteotome is used to create a unicortical window in the posterior tibia equal in size to the bony portion of the patellar tendon graft (Fig 7). The patellar tendon graft is inlaid and secured with a 6.5-mm titanium screw and spiked washer to the cancellous tibia1 bone. (Figs 8 and 9) When the tendinous portion of the graft is too long, the tibia1 insertion site may be advanced distally. If the meniscofemoral ligaments (Wrisberg and Humphrey) are incompetent, the peripheral lateral meniscus can be sutured to the PCL substitute (Fig 8). Postoperatively, the knee is braced in full extension for 2 weeks and the patient is partial weight bearing on crutches. Full weight bearing is allowed at 2 weeks with knee motion permitted over a 0” to 90” arc of motion. Isometric prone quadriceps exercises with the knee at 70” to 90” of flexion are started in physical therapy. At 6 weeks, the patient walks without crutches and prone quadriceps and hamstring exercises over a full arc of motion are begun. PRELIMINARY

RESULTS

Four patients whose ages averaged 32 years (range 27 to 36 years) at surgery had a PCL reconstruction in

the aforementioned manner (Table 1). All had contact mechanisms of injury. Three were the result of motor vehicle accidents and the fourth was caused by a fall from a tree. None of the reconstructions were performed acutely-the average time from injury to reconstruction was 14 months (range 5 to 25 months). Three of the four injuries were knee dislocations and had both cruciates and one collateral ligament torn. In one patient, the ACL was successfully repaired (negative pivot shift) by the referring physician. Therefore, two patients had PCL reconstructions in isolation and two had combined ACL/PCL reconstructions. No collateral ligament had a reconstructive procedure. All four patients had a positive quadriceps active drawer test at 70” of flexion (QAD 70’).” When the QAD 70” was quantified by preoperative KT-1000 arthrometer measurements, there was an average normal-abnormal side difference of -6 mm (range -5 to -7 mm) of increased laxity. They also complained of patellofemoral symptoms with pain on arising from a chair, and ascending and descending stairs. Preoperative University of Minnesota patellofemoral scores18 averaged 36.5 (range 24 to 47; loo-point maximum).

POPLITEAL

A.

FIG 6. The plane between semimembranous and the medial head of the gastrocnemius is bluntly developed. The tendon of the medial gastrocnemius head is incised and retracted laterally with its tibia1 nerve motor branch. The inferior medial geniculate artery and vein are identified at the superior margin of the popliteus muscle and ligated. (Inset) The popliteal oblique ligament and posterior capsule are incised. The tibia1 PCL insertion is visualized and the posterior tibia exposed subperiosteally.

PCL TIBIAL INLAY RECONSTRUCTION

73

femoral interosseous tunnels are fashioned from an anterior approach. ‘JNS’ The popliteal neurovascular structures are protected in a blind or semiblind fashion. Because the anterior knee approach is used in total knee arthroplasty, arthroscopy, and ACL reconstruction, its preference in PCL surgery may be a reflection of its familiarity to surgeons. Hem-y, in his classic description of the posterior knee approach,22 called it a “no man’s land” ripe for neurovascular complications. Another disadvantage of the popliteal fossa exposure

FIG 7. The knee is fully extended and slight traction is placed on the PCL graft after femoral fixation. An awl can be used to temporarily secure the graft and test the construct with a drawer maneuver. A unicortical posterior tibia1 window equal in size to the bony portion of the patellar tendon graft is made with an osteotome.

Operative findings confirmed interstitial midsubstance PCL tears and all had concomitant patellofemoral arthritis (Table 1). At a minimum 2-year follow-up, the KT-lOOO-measured QAD 70” improved in all four patients. The mean postoperative normal-abnormal side difference was -2 mm (range - 1 to -3 mm). Intrapatient improvement averaged 4 mm (range 3 to 5.5 mm). There was no loss of terminal extension postoperatively; however, terminal knee flexion averaged 11” (range 0” to 20”) less than the normal side. Two-year follow-up radiographs showed no evidence of fixation failure, implant migration, or acceleration of arthritic changes (Fig 9). All patients claimed subjective improvement in their knee function (Table 2). The average postoperative patellofemoral score doubled to 77 points (range 69 to 80). The mean intrapatient patellofemoral score improvement was 40.5 points (range 27 to 55 points) over preoperative values.

DISCUSSION Most of the currently described PCL reconstructions are modeled after ACL procedures in which tibia1 and

FIG 8.

The patellar tendon bone block is inlaid within window and secured to cancellous bone with a 6.5mm screw and spiked washer. If the meniscofemoral ligament petent, the peripheral lateral meniscus can be sutured to substitute.

the tibia1 titanium is incomthe PCL

74

E. E. BERG

FIG 9. (A) Anterior-posterior and (B) lateral knee radiographs 2 years after a combined anterior ACL autograft-PCL allograft reconstruction of patient K.C.

is the recommendation that the patient be positioned prone, 22-26which limits access to the remainder of the joint, especially with an arthroscope. All of the advantages of traditional anterior knee surgery (autogenous patellar tendon harvest, arthroscopic meniscal surgery, and ACL reconstruction) are maintained in the decubitus patient position, which also allows for concomitant posterior knee exposure.

That ligaments are physiologically loaded in tension has led many biomechanical investigators to use distractive models of interstitial ligament failure.9~L5~27-31 There is a growing body of evidence suggesting that many cruciate ligament failures are due to amputative phenomena.32”4 It has been shown with strong statistical power that bilateral, noncontact ACL tears occur in patients with stenotic intercondylar notches.“*‘* The late failures of ACL reconstructions with synthetic materials of adequate tensile strength but poor abrasion characteristics suggest that cruciate ligament reconstructions must be designed to avoid abrasive stresses.13-16 There is little direct evidence in the literature that PCL reconstructions fail from abrasion. In a 1983 article, Clancy et aL2 using a l-cm strip of patellar tendon autograph for PCL reconstruction, reported 92% excellent or good clinical results at 2-year follow-up. However, in his textbook treatise on PCL reconstructions, written 5 years later in 1988, Clancy’ describes doubling the collagenous bulk of the ligament substitute as a “major technical advance.” One must surmise that the additional PCL graft material was needed because of a discouraging incidence of late graft failures. The strain studies of Noyes et al9 measured the average maximum load to failure of the ACL to be 1,725 N. The commonly used central third patellar tendon graft measured a much higher 2,900 N maximum load to failure.’ In the independent studies of Race and Amis3’ and Prietto et a13’ the load to failure of the posterior cruciate ligament was slightly less than that of the ACL and measured between 1,500 and 1,630 N. Thus, a IOmm patellar tendon graft should have adequate tensile strength for a PCL reconstruction. Could the oblique tibia1 tunnel wall with abrasion at the “killer turn” have prompted the need to double the amount of graft collagen in PCL reconstruction? A major advantage of the popliteal fossa exposuretibia1 inlay technique is that the problems of ligament graft-tunnel margin abrasion are avoided and the Sharpey’s insertional fibers on the bone graft are preserved. The posterior knee arthrotomy with tibia1 inlay fixation allows for easier tensioning of the PCL graft as boundary friction between the extensive tibia1 tunnel wall and the soft-tissue-ligament substitute is obviated. Finally, although not a reported surgical complication, dual l-cm diameter tibia1 tunnels for a combined ACL/PCL reconstruction fashioned from an anterior approach could weaken the proximal tibia and predispose it to fracture. This is less of a problem with the inlay PCL reconstruction.

PCL TIBIAL TABLE

INLAY RECONSTRUCTION

1. Preoperative

and Intraoperative

75

Clinical

Data Chondromalacia*

Date of Injury

Job

Mech of Injury

Date of Surgery

Time to Surgery 9 mo

Name

Age

J.W.

35

Oil distributor

l/1/90

MVA

10/3/90

K.C.

30

Machine operator

9/88

MVA

8/8/90

2 yr

D.H.

27

Salesman

1 l/12/86

MVA

5/6/88

If yr

G.T.

36

Tree

1 l/23/89

Fall

419190

surgeon

* Outerbridge classification,” lesions > lf cm diameter. t Affecting the medial and lateral patellar facets. Abbreviations: MVA, motor vehicle accident; MCL, medial internal fixation; HO, heterotopic ossification.

difference)*

Postop

-6 mm -7 mm -5 mm -6.5 mm

-3 mm -2.5 mm -2 mm -1 mm

FN

Partial lat meniscectomy

2 Yr

II-111t

II

HO, LCL

2 yr

II-Ill?

Ill

5 mo

PCL MCL

11-111 med facet

ORIF lat tib plateau, ACL repair (femoral) Partial lat. meniscectomy HO, MCL

collateral

ligament;

U of M Patellofemoral

LCL,

lateral

-

collateral

ligament;

ORIF,

origin

open

Clinical

2 Yr

reduction

Data

Scores? Lysholm Scores”’

Postop

Postop

ROM

Improvement

Sub

Func

Total

Sub

Func

Total

Preop

Postop

Injury

Normal

3 mm 4.5 mm 3 mm 5.5 mm

10 16 23 18

14 17 19 29

24 33 42 47

36 40 33 42

43 40 36 38

79 80 69 80

51 28 39 74

92 83 61 94

O”- 125” O”- 125” on-120 -7”.140”

0”. 140” O”-135” O”-140 -7”.140”

* QAD 70” quadriceps active drawer in 70” of knee flexion.” t University of Minnesota Patellofemoral Scores 100 point maximum.‘x Abbreviations: ROM, range of motion; sub, subjective; Func, functional

4 yr

with its precision of femoral tunnel placement and facility with meniscal surgery. The posterior arthrotomy permits accurate placement of the tibia1 PCL insertion without the technical difficulties involved in the limited semiblind approach to the posterior aspect of the knee. Finally, the inlay bone block technique used to secure the tibia1 portion of the patellar bone-tendon-bone PCL graft permits easier ligament tensioning, a minimal exposure to abrasive phenomena, and maintains the biology of the Sharpey fiber-tendon-bone transition zone. It is hoped that the PCL inlay technique with its decreased soft-tissue graft-tunnel wall abrasion will improve graft longevity.

2. Postoperative

Preop Preop

or

Ill

In summary, this tibia1 inlay PCL reconstruction embraces the advantages of anterior arthroscopic surgery

(NL-ABN

Patella

Other Procedures Findings

1vt

CONCLUSION

KT- 1000 QAD

Femoral Trochlear Groove

ACL PCL MCL ACL PCL LCL PCL (ACL, MCL were successfully repaired)

In this small series of patients with disparate ligamentous lesions and a minimum 2-year follow-up, 10 mm of patellar tendon was sufficient to reconstruct the ligament. The arthrometrically measured QAD improved an average 4 mm to within -2 mm of the normal side. Patients lost a mean of 11” of terminal knee flexion and had improvement of patellofemoral scores.

TABLE

Injured Ligaments

components.

Thigh Atrophy 1 cm 1 cm 2 cm 0

E. E. BERG Acknowledgment: The author thanks Kathi Quigley, R.N., B.S.N., Sue Hilfer, Mark Taylor, and Vi&e Perronteau for their assistancewith this study and manuscript.

16. 17.

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