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The American Journal of Sports

http://ajs.sagepub.com/content/39/10/2187The online version of this article can be found at:

DOI: 10.1177/0363546511416597

2011 39: 2187 originally published online August 9, 2011Am J Sports MedJin Hwan Ahn, Tae Soo Bae, Ki-Ser Kang, Soo Yong Kang and Sang Hak Lee

Knee Significantly Influences Anterior StabilityDeficiengitudinal Tear of the Medial Meniscus Posterior Horn in the Anterior Cruciate Ligament

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Longitudinal Tear of the Medial MeniscusPosterior Horn in the Anterior Cruciate

LigamentDeficient Knee SignificantlyInfluences Anterior Stability

Jin Hwan Ahn,* MD, Tae Soo Bae,y PhD, Ki-Ser Kang,z MD,Soo Yong Kang,z MD, and Sang Hak Lee,|| MDInvestigation performed at Department of Orthopaedic Surgery, Center for JointDiseases and Rheumatism, Kyung Hee University Hospital at Gangdong, Seoul, Korea

Background: Longitudinal tears of the medial meniscus posterior horn (MMPH) are commonly associated with a chronic anterior

cruciate ligament (ACL) deficiency. Many studies have demonstrated the importance of the medial meniscus in terms of limiting

the amount of anterior-posterior tibial translation in response to anterior tibial loads in ACL-deficient knees.

Hypothesis: An MMPH tear in an ACL-deficient knee increases the anterior-posterior tibial translation and rotatory instability. In

addition, MMPH repair will restore the tibial translation to the level before the tear.

Study Design: Controlled laboratory study.

Methods: Ten human cadaveric knees were tested sequentially using a custom testing system under 5 conditions: intact, ACL

deficient, ACL deficient with an MMPH peripheral longitudinal tear, ACL deficient with an MMPH repair, and ACL deficient with

a total medial meniscectomy. The knee kinematics were measured at 0, 15, 30, 60, and 90 of flexion in response to a 134-N

anterior and 200-N axial compressive tibial load. The rotatory kinematics were also measured at 15 and 30 of flexion in a com-

bined rotatory load of 5 Nm of internal tibial torque and 10 Nm of valgus torque.

Results: Medial meniscus posterior horn longitudinal tears in ACL-deficient knees resulted in a significant increase in anterior-

posterior tibial translation at all flexion angles except 90 (P\ .05). An MMPH repair in an ACL-deficient knee showed a significant

decrease in anterior-posterior tibial translation at all flexion angles except 60 compared with the ACL-deficient/MMPH tear state

(P\ .05). The total anterior-posterior translation of the ACL-deficient/MMPH repaired knee was not significantly increased com-pared with the ACL (only)deficient knee but was increased compared with the ACLintact knee (P . .05). A total medial menis-

cectomy in an ACL-deficient knee did not increase the anterior-posterior tibial translation significantly compared with MMPH tears

in ACL-deficient knees at all flexion angles (P. .05). In a combined rotatory load, tibial rotation after MMPH tears or a total medial

meniscectomy in an ACL-deficient knee were not affected significantly at all flexion angles.

Conclusion: This study shows that an MMPH longitudinal tear in an ACL-deficient knee alters the knee kinematics, particularly

the anterior-posterior tibial translation. MMPH repair significantly improved anterior-posterior tibial translation in ACL-deficient

knees.

Clinical Relevance: These findings may help improve the treatment of patients with ACL and MMPH longitudinal tear by suggest-

ing that the medial meniscal repairs should be performed for greater longevity when combined with an ACL reconstruction.

Keywords: anterior cruciate ligament; medial meniscus posterior horn tear; meniscal repair

Meniscal injuries associated with acute anterior cruciate

ligament (ACL) tears are reported to range from 15% to

40%, and become much higher with a chronic ACL defi-

ciency.13 Several researchers have demonstrated that lon-

gitudinal tear of the medial meniscus posterior horn

(MMPH) around the meniscocapsular junction is found fre-

quently in knees with chronic deficient ACLs.8,19,25 More

than 75% of medial meniscal (MM) tears in ACL-deficient

knees occur in the peripheral posterior horn according to

a prospective analysis of 575 meniscal tears by Smith

and Barrett.23 However, many surgeons overlook this com-

bined tear because of the poor visualization and benign

appearance of the posterior meniscocapsular junction of

the MM from the anterior portals.1,3 Furthermore,

MMPH peripheral rim tears may heal slowly despite the

rich vascular supply to the red-red zone because the torn

meniscus has some movement proximally against the

meniscocapsular junction.2,3,19A recent clinical study dem-

onstrated that the rate of poor results of repair for MM

The American Journal of Sports Medicine, Vol. 39, No. 10

DOI: 10.1177/0363546511416597 2011 The Author(s)

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tears remains high when nonoperative treatment is used,

even though the nonoperative approach is more effective

for lateral meniscal tears.19,27

Biomechanical studies have demonstrated the impor-

tance of the meniscus, particularly the medial, in stabiliz-

ing the knee joint in chronically ACL-deficient knees.5,15,22

Furthermore, many authors have demonstrated the impor-

tance of the MM in limiting the anterior tibial translation

in response to anterior tibial loads in ACL-deficient

knees.4,17 Papageorgiou et al17 reported that the resulting

forces on the MM were increased by as much as 200% in

response to anterior tibial loads after the ACL had been

transected. Furthermore, they demonstrated a 33% to

50% increase in the in situ forces in the ACL replacement

graft after a medial meniscectomy. More recently, Seon

et al20 confirmed that a subtotal medial meniscectomy in

an ACL-deficient knee increased significantly the anterior

and lateral tibial translations. These results prompted sev-

eral authors to recommend that an ACL-deficient knee be

reconstructed to protect the menisci.7,18,28

The purpose of this study was to quantify the effects ofMMPH longitudinal tears and meniscal repair on ACL-

deficient knees. It was hypothesized that an MMPH tear

in an ACL-deficient knee would increase the anterior-pos-

terior (A-P) tibial translation and combined rotational lax-

ity. It was also hypothesized that MMPH repair could

restore the tibial translation to the level before the menis-

cal tear.

METHODS

Specimen Preparation

Ten fresh-frozen, nonpaired human cadaveric knees, rang-

ing in age from 34 to 74 years (mean, 58 years), were used

in this study. Six were from male donors, and 4 were from

female donors. All knees were macroscopically intact and

showed no evidence of prior surgery, structural abnormal-

ities, or arthritic changes according to a clinical examina-

tion. The specimens were kept frozen at 20C before the

tests and were thawed at room temperature overnight

before the experiment. The knees were dissected carefully,

removing the skin and soft tissue, and leaving the popli-

teus muscle, joint capsule, ligamentous structures, and

surrounding retinaculum intact. The fibular head was

transfixed to the tibia by a 6.5-mm cannulated screw and

spiked washer (Jeil Meditec, Daegu, Korea) to maintainits anatomic position and then the distal part was excised.

The femur and tibia were then sectioned at approximately

25 cm in length from the joint line and secured in thick-

walled aluminum cylinders using denture acryl (Vertex,

Dentimex BV, Zeist, The Netherlands). Care was taken

to center the long axis of the bone within the cylinder,

which is representative of the long axis of the bones. The

knees were protected from dehydration by the intermittent

applications of physiological saline during preparation and

testing periods.

Kinematic Measurements

To measure the kinematics of the knee, each specimen was

mounted firmly in an Instron testing machine (Instron

850I, MTS, Minneapolis, Minnesota). A custom knee jig

was used to hold the denture acrylic potted bone. The potted

bones were then bolted securely within the jigs. The jig

allowed rigid fixation of the femur but provided 5 degrees

of freedom at the tibia (anteroposterior and proximal-distal

translations; and varus-valgus, internal-external rotations,

and flexion-extension). The custom testing jig was specifically

designed with a pulley system to accommodate the manual

application of an anterior and posterior tibial load, as well

as a varus and valgus torque. The application of a load was

achieved by hanging weights from a cable and pulley system.

The experimental setup provided control over various knee

flexion angles, which were confirmed using a protractor

attached to the jig. The tibial kinematic measurements

were obtained to the nearest tenth of a millimeter using elec-

tronic calipers. Two optical encoders in the joints recorded

the varus-valgus rotational laxity and internal-external rota-

tional laxity of the tibia. Because of the challenges inherent

in defining the physiologic neutral position of the cadaveric

knee, the laxity measurements were defined as the resultant

A-P tibial translation, varus-valgus rotational laxity, and

internal-external rotational laxity of the tibia relative to

the femur when the appropriate force was applied.

Testing Protocol

A custom testing system was sequentially tested under 5

conditions: intact, ACL deficient, ACL deficient with

MMPH peripheral longitudinal tear, ACL deficient with

an MMPH repair, and ACL deficient with a total medial

meniscectomy (Table 1). The knee kinematics were mea-

sured at 0, 15, 30, 60, and 90 of flexion, while the posi-

tions of the knee, which minimized all external forces and

moments applied to the joint throughout the range of flex-

ion from 0 to 90, were recorded. These positions, at which

the knee was effectively unloaded, served as starting

points for the application of an external load as well as

the reference points for the measurements of the kneekinematics throughout each test. The difference between

the starting point and the end point position was calcu-

lated for each test performed for each sectioned state and

flexion angle. The externally applied loading condition in

this study combined 2 forces: 134-N anterior and 200-N

axial compressive tibial load at full extension and 15,

Address correspondence to Sang Hak Lee, MD, Department of Orthopaedic Surgery, Center for Joint Diseases and Rheumatism, Kyung Hee Univer-

sity Hospital at Gangdong, 892 Dongnam-ro, Gangdong-gu, Seoul, 134-727, Korea (e-mail: [email protected]).

*Department of Orthopaedic Surgery, Sungkyunkwan University School of Medicine, Kangbuk Samsung Hospital, Seoul, Korea.yKorea Orthopedics & Rehabilitation Engineering Center, Inchon, Korea.zDepartment of Orthopaedic Surgery, Chung-Ang University, School of Medicine, Seoul, Korea.||Center for Joint Diseases and Rheumatism, Kyung Hee University Hospital at Gangdong, Seoul, Korea.

The authors declared that they have no conflicts of interest in the authorship and publication of this contribution.

2188 Ahn et al The American Journal of Sports Medicine



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30, 60, and 90 of flexion. The combined rotatory kine-

matics were also measured at 15 and 30 of flexion in

a combined rotatory load of 5 Nm of internal tibial torque

and 10 N

m of valgus torque (Figure 1). Under each ofthese loads, the testing system manipulated the knee joint

in 4 degrees of freedom (with a constant selected flexion

angle) until the applied forces were balanced by the knee.

After the kinematics in the intact knee was determined,

the ACL was transected to represent an ACL-deficient con-

dition through a 5-cm longitudinal anteromedial arthrot-

omy. The MMPH peripheral longitudinal tear was made

from the posterior horn to the posteromedial corner at

the meniscocapsular junction through a 5-cm longitudinal

posteromedial arthrotomy (Figure 2). The mean length

of the longitudinal tears measured 2.8 cm (range,

2.4-3.3 cm). The root of the MMPH and midbody of the

MM were preserved in our experimental protocol. The

arthrotomy was repaired in layers by sutures with

2-0 Vicryl suture material. In the next step, the MMPH

tear was repaired using absorbable sutures (No. 0 PDS

[polydioxanone], Ethicon, Somerville, New Jersey). Every

stitch was made with a roughly 4- to 5-mm interval using

a vertically oriented repair technique. Thus, the MMPH

tear in each specimen was repaired by 4 to 5 stitches. Finally,

a total resection of the entire MM, removing the inner portion

of the whole body and the posterior horn, was performed

through the same posteromedial arthrotomy. The arthrotomy

was closed carefully in layers in each step. The external load

was then reapplied with each step and the resulting kinemat-

ics recorded using the testing system. Each knee was tested 2

times at each flexion angle and the results were averaged.

The mean difference between the origin and the end point

position was calculated for each test performed for each sec-

tioned state flexion angle.

Statistical Analysis

The knee laxity measurements were repeated for 2 trials

and the mean value was used for data analysis. The

TABLE 1

Experimental Protocol and Data Acquireda

Protocol Data Acquired

I. Intact joint

External loading conditions Intact joint kinematics at all flexed angles:

A. 134-N anterior tibial load (1) anterior tibial translation

B. 200-N axial compressive tibial load (2) valgus-varus angle

(3) internal-external rotations

Combined rotatory load (apply loads A and B) Intact joint kinematics at 15 and 30 of flexion:

C. 10 Nm of valgus load (4) internal-external rotations

D. 5 Nm of internal tibial torque

II. ACL-deficient joint

Transect ACL

Apply loads A and B ACL-deficient joint kinematics at all flexed angles(1), (2), (3)

Apply loads A, B, C, and D ACL-deficient joint kinematics at 15 and 30 of flexion(4)

III. MMPH tear with ACL-deficient joint

Make MMPH peripheral longitudinal tear



IV. MMPH repair with ACL-deficient joint

Repair MMPH tear Apply loads A and B ACL-deficient joint kinematics at all flexed angles(1), (2), (3)


V. Total medial meniscectomy with ACL-deficient joint

Perform total medial meniscectomy



a ACL, anterior cruciate ligament; MMPH, medial meniscus posterior horn.

Figure 1. Schematic illustration of testing systems with

a right cadaveric knee specimen.

Vol. 39, No. 10, 2011 Medial Meniscus Posterior Horn Tear and Knee Stability 2189



5/8

reliability of measurements was assessed by the intraclass

correlation coefficient (ICC), which quantifies the propor-

tion of the variance attributable to variability between

measurements. Because all variables were measured within

each specimen, statistical analysis of the knee kinematics

was performed using a Friedman test with Bonferroni cor-

rection or 2-way analysis of variance. All statistical analyses

were carried out using SAS version 9.13 software (SAS

Institute Inc, Cary, North Carolina). P values \ .05 were

considered significant.

RESULTS

The ICC for test-retest reliability of the measurement was

greater than 0.9, ranging from 0.99 to 0.92, for all meas-

urements. This value indicated that all measurements

had excellent reproducibility.

Knee Kinematics in Response to 134-N Anterior

and 200-N Compressive Tibial Load

When a combined 134-N anterior and 200-N axial compres-

sive tibial load was applied, the A-P tibial translation of the

ACL-intact knee ranged from 7.16 0.9 mm at full extension

to 9.0 6 2.9 mm at 30 of flexion (Figure 3, Table 2). The

largest A-P tibial translation of the ACL-intact knee was

observed at 15 and 30 of flexion as 8.6 6 2.1 mm and

9.0 6 2.9 mm, respectively. After the ACL was resected,

the A-P tibial translation under combined loads in the

ACL-deficient knees was significantly larger than in the

intact knee at all flexion angles selected (P\ .05). Medial

meniscus posterior horn tears in the ACL-deficient knees

resulted in an additional increase in A-P tibial translation

at all flexion angles except 90 (P\ .05). These increases

in A-P tibial translation differed according to the flexion

angle, from a minimum of 1.7 6 0.8 mm at 90 of flexion

to a maximum of 5.2 6 1.2 mm at 15 of flexion. Medial

meniscus posterior horn repair in the ACL-deficient knee

reduced A-P tibial translation significantly at all flexion

angle except 60 (P \ .05). After MMPH repair in the

ACL-deficient knee, the A-P tibial translation was not sig-

nificantly increased compared with the ACL-onlydeficient

knee at all flexion angles (P . .05). Furthermore, a total

medial meniscectomy in the ACL-deficient knees did not

increase the A-P tibial translation significantly compared

with the MMPH peripheral tears in the ACL-deficient knee

at all flexion angles, which ranged from 11.3 6 6.3 mm at

90 of flexion to 19.5 6 5.9 mm (P . .05).

The coupled varus-valgus and internal-external rota-tions in response to the combined 134-N anterior and

200-N axial compressive tibial load were also measured

and are shown Tables 3 and 4. Both varus-valgus and

internal-external rotations in ACL-deficient knees were

not affected significantly by the MMPH tears or total

medial meniscectomy at all flexion angles (P . .05).

Knee Kinematics in Response to a

Combined Rotatory Load

The resulting internal-external tibial rotation in response

to a 5-Nm internal tibial torque with a 10-Nm valgus tor-

que was increased by each step: the ACL resection, MMPHtear, and total medial meniscectomy at 15 and 30 of knee

flexion although there were no significantly differences

(P . .05). The resulting tibial rotation was decreased by

MMPH repair in the ACL-deficient knee at 15 and 30

of knee flexion. However, no statistically significant differ-

ences also could be found at any flexion angle among each

step at 15 and 30 of knee flexion (P . .05) (Table 5).

DISCUSSION

The effect of an MMPH longitudinal tear in ACL-deficient

knees on the kinematics of the knee has not been reported.

This biomechanical study showed that an MMPH

Figure 2. Schematic drawings show that a peripheral longi-

tudinal tear of the medial meniscus posterior horn (MMPH)

was made from the posterior horn to the posteromedial cor-

ner at the meniscocapsular junction (A) and the MMPH tear

was repaired using absorbable sutures (B).

Figure 3.Anterior translation of the tibia under anterior andcompressive tibial load in 5 different knee conditions. Statis-

tical significances were noted between intact and anterior

cruciate ligament (ACL) resect groups, ACL resect and ACL

resect 1 meniscus tear groups, and ACL resect 1 meniscus

tear and ACL resect 1 meniscus repair groups at most flex-

ion angles. An asterisk represents statistical significance

(P\ .05); error bars represent the standard deviation.




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longitudinal tear in ACL-deficient knees increased the ante-

rior translation of the tibia. Medial meniscus posterior hornrepair using an absorbable suture material in an ACL-defi-

cient knee reduced A-P tibial translation significantly at

most flexion angles. In addition, no significant difference

was observed between the total medial meniscectomy and

MMPH longitudinal tear in the A-P tibial translation of

the tibia. In this study, an MMPH longitudinal tear in the

ACL-deficient knee resulted in similar kinematic changes

to that with a total medial meniscectomy under a combined

anterior and axial compressive tibial load.

The meniscal tear patterns that occur in ACL-deficient

knees have been studied widely. Cerabona et al6 reported

that in 50 patients, most of the medial meniscal tears were

peripheral and posterior. Indelicato and Bittar

10

also

demonstrated that most medial meniscal tears in ACL-defi-

cient knees were peripheral posterior horn tears. Morerecently, Smith and Barrett23 prospectively studied 575

meniscal tears to evaluate the locations of meniscal tears

associated with ACL injuries. They found that peripheral pos-

terior horn tears of the medial meniscus were the most com-

mon type of tear (230 of 575 [40%]) by a statistically

significant amount. These findings are in agreement with

most theories suggesting that peripheral posterior horn tears

are caused by the recurrent trauma sustained by the MM

while acting as a bumper in the ACL-deficient knee. There-

fore, this study focused on MMPH tears in ACL-deficient

knees. The data conclusively show that MMPH tears in

ACL-deficient knees alter the knee kinematics, particularly

the anterior translation.

TABLE 2

Mean Values (6Standard Deviation) of Anterior Translation (mm) of the Tibia

Under 134-N Anterior and 200-N Compressive Tibial Load in 5 Different Knee Conditionsa

Knee Condition 0 15 30 60 90

Intact 6.9 6 0.9 8.6 6 2.1 9.0 6 2.9 7.1 6 1.9 6.6 6 2.0

ACL resect 10.16

1.9

b

14.26

3.6

b

14.86

4.7

b

11.86

2.2

b

8.96

3.2

b

ACL resect/MMPHT 13.96 2.4c 18.7 6 4.8c 16.8 6 4.8c 13.9 6 3.7c 9.8 6 4.1

ACL resect/MMPHR 12.06 2.2d 15.6 6 3.7d 14.8 6 4.4d 12.4 6 4.3 8.1 6 3.9d

ACL resect/TMM 13.66 4.1e 18.8 6 6.1e 16.9 6 5.5e 14.6 6 5.7e 9.8 6 6.2e

aACL, anterior cruciate ligament; MMPHT, medial meniscus posterior horn tear; MMPHR, medial meniscus posterior horn repair; TMM,

total medial meniscectomy.bP\ .05 when compared with the intact knee.cP\ .05 when compared with the ACL-resected knee.dP\ .05 when compared with the ACL-resected/MMPHT knee.eP\ .05 when compared with the ACL-resected/MMPHR knee.

TABLE 3

Mean Values (6Standard Deviation) of Valgus-Varus Angle (deg) of the Tibia



Intact 0.2 6 1.1 0.5 6 1.0 0.8 6 1.6 0.6 6 0.9 1.2 6 2.0

ACL resect 1.26 0.7 1.6 6 2.6 2.7 6 3.7 3.0 6 3.4 2.2 6 2.9

ACL resect/MMPHT 1.56 2.8 0.5 6 6.3 2.6 6 3.4 3.2 6 4.3 1.7 6 4.2

ACL resect/MMPHR 0.36 1.8 2.6 6 4.0 3.4 6 4.0 3.4 6 4.6 1.6 6 3.4

ACL resect/TMM 0.66 1.4 0.5 6 2.6 2.5 6 6.8 0.3 6 6.2 1.0 6 6.8

aThere were no significant differences between the groups at all selected flexion angles. ACL, anterior cruciate ligament; MMPHT, medial

meniscus posterior horn tear; MMPHR, medial meniscus posterior horn repair; TMM, total medial meniscectomy.

TABLE 4

Mean Values (6Standard Deviation) of Internal Rotation Angle (deg) of the Tibia



Intact 2.3 6 2.5 4.9 6 3.9 5.3 6 5.3 3.7 6 3.0 3.3 6 2.9

ACL resect 1.36 1.4 3.2 6 3.7 1.7 6 3.9 0.7 6 3.2 0.2 6 3.3

ACL resect/MMPHT 1.06 1.1 1.3 6 3.6 1.0 6 4.0 0.5 6 3.4 0.6 6 4.7

ACL resect/MMPHR 1.66 2.0 2.9 6 3.8 0.6 6 3.6 0.3 6 5.9 1.9 6 4.5

ACL resect/TMM 2.36 1.3 1.5 6 3.4 0.2 6 6.7 1.2 6 4.7 3.1 6 5.9

aThere were no significant differences between the groups at all selected flexion angles. ACL, anterior cruciate ligament; MMPHT, medial

meniscus posterior horn tear; MMPHR, medial meniscus posterior horn repair; TMM, total medial meniscectomy.




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An anterior tibial load of 134 N was chosen because the

ACL is a major restraint to the anterior tibial translation

and it simulates clinical tests, such as the Lachman or ante-

rior drawer tests, which are commonly used for diagnosingan ACL injury.15 Another important physical examination

of an ACL injury and reconstruction is the pivot-shift test,

during which a combined internal and valgus torque is

applied to the knee. Kanamori et al11 recommended the

application of low internal torque in combination with val-

gus torque to simulate a pivot-shift test when evaluating

ACL-deficient knee joints. Therefore, a 5-Nm internal tibial

torque and a 10-Nm valgus torque were used to simulate

the pivot-shift test. However, tibial rotation and valgus-

varus angle were not significantly changed after MMPH

tears or total medial meniscectomy. Furthermore, no signif-

icant differences were observed in the internal tibial rota-

tions under compressive tibial loads and combined rotatorloads among 5 knee conditions, although our data showed

a similar trend in tibial internal rotation after MMPH tear

in ACL-deficient knees. These results may suggest that

the combined internal and valgus torques are an inefficient

loading condition for investigating the rotational laxity in

cadaveric specimens.12 Comprehensive loading conditions

are required to truly assess the ability of the ACL and

MMPH to restrain tibial rotations. To more accurately

mimic in vivo loading conditions, larger forces such as those

from the quadriceps and hamstring muscles will be needed.

Some authors have reported that many acute stable

peripheral longitudinal meniscal tears with an acute

ACL injury either heal spontaneously or the symptoms

resolve without an extension of the tear in 58% to 69% of

cases.9,26 Shelbourne and Rask21 reported that of stable

peripheral vertical MM tears treated with abrasion and

trephination, most (94%) remain asymptomatic without

stabilization. However, 2 recent reports described different

healing results of medial or lateral meniscal tears left in

situ during an ACL reconstruction. Yagishita et al27

reported that the overall healing rate of 41 medial menis-

cal tears left without repair, including completely and

incompletely healed tears, was significantly lower than

that of 42 lateral meniscal tears (61% vs 79%). Pujol and

Beaufils19 also reported that the high prevalence of fail-

ures of medial meniscal tears left in situ during an ACL

reconstruction raises concern, even though a conservative

approach is more effective for the lateral meniscus. Previ-

ous reports1,3 showed that a torn posterior meniscocapsu-

lar structure moved inferiorly against the remaining

meniscus, displacing the tear during knee flexion. This

motion of the torn MM can partially explain the slow heal-

ing observed in MMPH peripheral rim tears despite the

rich vascular supply to the red-red zone. Therefore, we rec-

ommend that MMPH tears in ACL-deficient knees be trea-

ted more aggressively using a vertically oriented suturing

technique that was previously reported,1,3 an arthroscopic

modified all-inside suture technique of Morgan et al16

using 2 posteromedial portals. Absorbable meniscal fixa-

tors are not believed to be sufficient for this type of tear

because these tears require secure fixation to the capsule,

which cannot be provided by the new bioabsorbable devi-

ces. Previous clinical reports reported a clinical success

rate of 96.4% (135 of 140) for modified all-inside meniscal

repairs with a concomitant ACL reconstruction.2 The pres-

ent study also demonstrated that vertically oriented

MMPH repairs in ACL-deficient knees reduced A-P tibialtranslation significantly at all flexion angles except 60 to

a level not increased significantly, compared to the ACL-

onlydeficient knee at all flexion angles.

Many studies have reported the important stabilizing

role of the MM. In 1982, Levy et al14 demonstrated that

the posterior horn of the MM as a mechanical block contrib-

uted significantly to restraining the primary anterior trans-

lation of the knee after sectioning of the ACL. The work by

Sullivan et al24 in 1984 supports this concept. As a result,

the present belief of many researchers is that the MM is

a secondary restraint to an A-P tibial translation that

becomes much more important with the loss of ACL func-

tion. More recently, Seon et al20

showed the effect of an ACL reconstruction on the kinematics of the knee with

a combined ACL deficiency and subtotal meniscectomy

under anterior tibial and simulated quadriceps loads. Their

study demonstrated that a subtotal medial meniscectomy in

ACL-deficient knees increased the A-P tibial translation

and lateral shift of the tibia. The present study showed

that MMPH longitudinal tears in an ACL-deficient knee

resulted in similar kinematic changes with a total medial

meniscectomy under a combined anterior and axial com-

pressive tibial load. Therefore, MMPH longitudinal tears

should be repaired in the setting of an ACL reconstruction

to restore the optimal knee kinematics and function.

This study had some limitations. First, the biomechani-

cal test setup was obtained only for time-point zero, without

the possibility of taking the influence of muscle function into

consideration. And the testing setup is not 6 degrees of free-

dom load cell with a robotic testing system. However, the

ICC for test-retest reliability of the measurement was

greater than 0.9, ranging from 0.99 to 0.92, for all measure-

ments. Further research will be directed to evaluate this

testing protocol under simulated muscle load and in the

in vivo situation. Second, an open technique was used to

resect the ACL and perform MMPH tear, MMPH repair,

and medial meniscectomy procedures. Although the incision

and repair of the arthrotomy were performed carefully to

avoid potential bias from changes in capsular tension, the

TABLE 5

Mean Values (6Standard Deviation) of Internal Rotation

Angle (deg) of the Tibia Under Combined Rotatory Load

in 5 Different Knee Conditionsa

Knee Condition 15 30

Intact 7.96

4.4 8.86

4.6 ACL resect 10.26 5.1 10.8 6 5.9

ACL resect/MMPHT 13.06 5.7 12.9 6 7.0

ACL resect/MMPHR 9.96 4.9 8.8 6 4.0

ACL resect/TMM 12.86 6.8 11.0 6 5.3

aThere were no significant differences between the groups at all

selected flexion angles. ACL, anterior cruciate ligament; MMPHT,

medial meniscus posterior horn tear; MMPHR, medial meniscus

posterior horn repair; TMM, total medial meniscectomy.




8/8

open technique, particularly a posteromedial arthrotomy,

may affect the knee kinematics in rotation and posterior

translation. Third, these tests were performed in older

cadaveric knee specimens. A different pattern of ligamen-

tous versus bony injury may be seen in younger knees, rep-

resenting the typical patient population that may sustain

these types of injuries. Fourth, this is a cadaveric in vitro,

time-zero study; therefore, we are unable to determine the

effects of biologic processes on the suture material fixation

and meniscal healing in vivo. Furthermore, our design facil-

itated a repeated-measures analysis of kinematics using the

same specimen under different loading conditions. This may

be influenced subsequently by the effects of chronic relaxa-

tion and stretching of specimen. Finally, the rate of stress

testing does not reproduce the rate of loading at the time

of the actual injury to the knee.

This study shows that an MMPH longitudinal tear in

an ACL-deficient knee alters the knee kinematics, partic-

ularly the anterior tibial translation. MMPH repair

reduces significantly the increased anterior tibial transla-

tion in ACL-deficient knees. These findings may helpimprove the treatment of patients with ACL and MMPH

longitudinal tears by suggesting that the MM repairs

should be undertaken for greater longevity of results

when combined with an ACL reconstruction.

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