Dale M. Daniel

Instrumented measurement of anterior laxity of the knee.

We performed instrumented measurement of anterior-posterior laxity of the knee in thirty-three cadaver specimens, 338 normal subjects, and eighty-nine patients with unilateral disruption of the anterior cruciate ligament. The test instrument was the Medmetric knee arthrometer, model KT-2000. We measured total anterior-posterior laxity, produced by anterior and posterior loads of eighty-nine newtons (twenty pounds), and the anterior compliance index. The total anterior-posterior laxity is composed of an anterior displacement and a posterior displacement; these are measured from a testing reference position, defined as the resting position of the knee after applying and then releasing a posterior load of eighty-nine newtons. The anterior compliance index is defined as the anterior displacement between an anterior load of sixty-seven newtons and one of eighty-nine newtons. All tests were performed with the knee held on a thigh support that placed the knee in 20 +/- 5 degrees of flexion. The mean anterior displacement at eighty-nine newtons was 5.7 millimeters in a group of normal subjects and 13.0 millimeters in a group of patients with a disrupted anterior cruciate ligament. Ninety-two per cent of the normal subjects had a left knee-right knee difference in anterior displacement of no more than two millimeters, while 96 per cent of the patients with a unilateral disruption of the anterior cruciate ligament had an injured knee-normal knee difference in anterior displacement of more than two millimeters. Ninety-three per cent of the normal subjects had a difference in the left-right compliance index of no more than 0.5 millimeter, and 85 per cent of the patients with unilateral disruption of the anterior cruciate ligament had a difference in the compliance index of the injured and normal sides of more than 0.5 millimeter.

Instrumented measurement of anterior knee laxity in patients with acute anterior cruciate ligament disruption

Instrumented anterior/posterior laxity measurements were performed on 138 patients evaluated within 2 weeks of injury with their first traumatic knee hemar throsis. All patients were tested with the MEDmetric Arthrometer model KT-1000 in a knee injury clinic. Seventy-five of the patients had knee arthroscopy. Thirty-three had arthrometer laxity tests under anes thesia. Eighty-seven percent of patients arthroscoped had anterior cruciate ligament (ACL) tears and 41 % had meniscus tears. One hundred twenty normal subjects were tested to establish normal anterior laxity values. Three tests were used to evaluate anterior laxity: anterior displacement between a 15 and 20 pound force (compliance index), anterior displacement with a 20 pound force, and an terior displacement with a high manually applied force. Displacement measurements in normal subjects re vealed a wide range of normal laxity with a small right knee-left knee difference. For example, the 20 pound anterior displacement range was 3 to 13.5 mm with a right knee-left knee difference (mean ± SD, 0.8 ± 0.7 mm). Eighty-eight percent of the normals had a right- left difference of less than 2 mm. In the 53 patients arthroscoped who had complete ACL tears, the anterior laxity measurements performed in the clinic were suggestive or diagnostic of pathologic anterior laxity in 50 patients.

Medial soft tissue restraints in lateral patellar instability and repair.

This study was undertaken to evaluate the medial ligamentous stabilizers of the patella in restraining lateral displacement and to assess their relative contribution after individual repair. Seventeen fresh frozen human anatomic specimen knee joints were studied. The specimens were loaded onto a testing instrument that was designed to measure the compliance of the medial and lateral patellar restraints in the coronal plane. Two different cutting and repair sequences were used to test the individual contributions of the patellar ligaments. The medial patellofemoral ligament was found to be the major medial ligamentous stabilizer of the patella. Isolated release resulted in a 50% increase in lateral displacement, and isolated repair restored balance to the patella. In addition, the patellotibial and patellomeniscal ligament complex played an important secondary role in restraining lateral patellar displacement. Isolated repair of these ligaments restored balance to near normal levels. The medial patellofemoral retinaculum played only a minor role in patellofemoral instability. Proximal realignment or medial ligament repair for patellofemoral instability specifically should address repair of the deep layers that contain the restraints to lateral patellar displacement. Failure to include these structures in repair, especially of the medial patellofemoral ligament, may lead to persistent or recurrent instability.

Prospective Trial of a Treatment Algorithm for the Management of the Anterior Cruciate Ligament–Injured Knee

Background Specific guidelines for operative versus nonoperative management of anterior cruciate ligament injuries do not yet exist. Hypothesis Surgical risk factors can be used to indicate whether reconstruction or conservative management is best for an individual patient. Study Design Prospective nonrandomized controlled clinical trial; Level of evidence, 2. Methods Patients were classified as high, moderate, or low risk using preinjury sports participation and knee laxity measurements. Early anterior cruciate ligament reconstruction (within 3 months of injury) was recommended to high-risk patients and conservative care to low-risk patients. It was recommended that moderate-risk patients have either early reconstruction or conservative care, according to the day of presentation. Assessment of subjective outcomes, activity, physical measurements, and radiographs was performed at mean follow-up of 6.6 years. Results Early phase conservative management resulted in more late phase meniscus surgery than did early phase reconstruction at all risk levels (high risk, 25% vs 6.5%; moderate risk, 37% vs 7.7%, P =. 01; low risk, 16% vs 0%). Early- and late-reconstruction patients’ Tegner scores increased from presurgery to follow-up (P <. 001) but did not return to preinjury levels. Early-reconstruction patients had higher rates of degenerative change on radiographs than did nonreconstruction patients (P <. 05). Conclusions Early phase reconstruction reduced late phase knee laxity, risk of symptomatic instability, and the risk of late meniscus tear and surgery. Moderate- and high-risk patients had similar rates of late phase injury and surgery. Reconstruction did not prevent the appearance of late degenerative changes on radiographs. Relationship between bone contusion on initial magnetic resonance images and the finding of degenerative changes on follow-up radiographs were not detected. The treatment algorithm used in this study was effective in predicting risk of late phase knee surgery.

Use of the quadriceps active test to diagnose posterior cruciate-ligament disruption and measure posterior laxity of the knee.

Orthopaedic surgeons routinely use passive tests, in which the displacing force is applied externally, to evaluate the integrity of the ligaments of the knee. Using a quadriceps active test, in which the muscle contractures of the subject served as the displacing force, tibial displacement was measured with an arthrometer in ninety-two subjects: sixty-seven who had an acute or chronic rupture of the posterior or anterior cruciate ligament and twenty-five who had normal knees. With the knee joint in 90 degrees of flexion, contraction of the quadriceps resulted in anterior translation of the tibia in forty-one of forty-two knees that had a documented disruption of the posterior cruciate ligament. This anterior translation did not occur in the contralateral, normal knee of the same subjects; in the knees of the twenty-five normal subjects; or in twenty-five knees that had a known unilateral anterior cruciate-ligament disruption.

Soft tissue fixation to bone

This experiment was designed to compare the imme diate fixation strengths of various methods of soft tissue fixation techniques. The fixation techniques tested were the barbed staple, stone staple, suture techniques, screw with spiked plastic washer, and the screw with spiked soft tissue plate. Cadaveric soft tissue specimens were classified into three distinct morphologic types: capsular, tendinous, and extensor mechanism tissue. Each specimen was fixed to bone by one of the fixation techniques. The specimens were loaded in a cyclical fashion until fixation failure occurred. One hundred thirty-seven trials were performed. The screws with the spiked plastic washer and soft tissue plate proved superior overall for all three tissue types. The stone staple was the poorest technique tested. Therefore, if cyclic loading or tension is anticipated at the fixation site, the fixation technique of choice would be the screw with spiked plastic washer or soft tissue fixation plate.

An in vitro study of anterior cruciate ligament graft placement and isometry

Isometric positioning of the ACL graft or prosthesis is an important consideration in successful reconstruction of the ACL-deficient knee. This study documented the relationship between graft placement and intraarticular graft length changes and graft tension changes during knee passive range of motion. Fifteen fresh cadaveric knees were mounted in sta bilizing rigs. The ACL was identified and cut in each specimen. Intraarticular reconstruction was then per formed using a 6 mm polypropylene braid (3M LAD, St. Paul, MN). The following graft placements were evalu ated : 1) over-the-top, 2) modified over-the-top with a femoral bone trough, 3) femoral drill hole positions, and 4) tibial drill hole positions. The proximal end of the graft was fixed to the lateral aspect of the femur with a screw and spiked washer. The distal end of the graft was attached to a turnbuckle attached to a load cell on the anterior aspect of the tibia. The knee was then extended passively from 90° to 0°. Two experiments were performed. In Experiment A, the turnbuckle was adjusted to keep graft tension constant and the graft length changes were recorded. In Experiment B, the graft fixation sites were not altered and tension changes with range of motion were recorded. A change in the graft distance between attachment sites with knee range of motion can be monitored either by ligament length or by tension change. With the over- the-top technique, in Experiment A, the graft distance between attachment sites increased as the knee was extended (x = 4.9 mm); in Experiment B, large tension increases were recorded with knee extension. With the modified over-the-top technique with femoral bone trough, isometry was approached as the average length increase with knee extension was reduced to 1.0 mm (Experiment A) and minimal tension increases occurred (Experiment B). Femoral drill holes positioned postero superiorly on the lateral femoral condyle produced vari able length or tension increases with knee extension. Anteriorly positioned femoral drill holes produced sig nificant length decreases with knee extension in Exper iment A (x = -5.5 mm) while tension measurements showed loss of graft tension with knee extension (Ex periment B). Finally, tibial drill hole position was also found to be vital for proper isometric tracking. Tibial drill holes situated immediately anterior to the antero medial portion of the ACL insertional site yielded the best isometric placement for the femoral orientations tested. Care must be taken, however, that this tibial position does not cause impingement in the intercon dylar notch.

The measurement of anterior knee laxity after ACL reconstructive surgery.

An objective clinical instrument known as a knee ligament Arthrometer was developed. The instrumentation system was applied to measurements of knee ligament laxity in the operating room with the patients under anesthesia. Prereconstruction and immediate postreconstruction measurements were made with the patient still on the operating table. The change in laxity of the patients operated knee as compared to the opposite nonoperated control knee was documented for 19 chronic and 24 acute patients. Four separate reconstruction types were studied in the operating room. The immediate postreconstruction measurements documented that all four of the reconstruction types were equally effective in the immediate restoration of normal laxity in the ACL-deficient knees. The Arthrometer proved to be a useful tool for confirming that each patients normal knee laxity was reestablished in the O.R. by its reconstruction.

The effect of tibial attachment site on graft impingement in an anterior cruciate ligament reconstruction

Anterior cruciate ligament reconstructions were per formed in 14 cadaveric knee specimens using a 6-mm wide polypropylene graft. The graft was passed through a femoral tunnel at the attachment site of the anterior medial bundle of the anterior cruciate ligament. Seven tibial positions were evaluated as to the change in attachment site distance with passive range of mo tion and impingement on the intercondylar notch as the knee was passively ranged from 0° to 90° of flexion. Impingement was also evaluated while the knee was extended by pulling through the quadriceps tendon. The tibial placement site affects the change in attach ment site distance with passive range of motion and impingement on the intercondylar notch. Grafts passed through drill holes anterior and lateral to the insertion of the anterior fibers of the anterior cruciate ligament consistently produced impingement on the anterior out let of the intercondylar notch. Knee extension with quadriceps tendon pull produced graft impingement in a greater arc of flexion than passive extension. Based on this study, optimum placement of the tibial hole should be at the insertion of the anterior medial fibers of the anterior cruciate ligament. Impingement recog nized during surgery can be alleviated with notchplasty. With passive extension there should be a 3-mm clear ance between the anterior portion of the intercondylar notch and the ligament graft to prevent the graft from impinging when the knee is actively extended.

Combined injuries of the anterior cruciate and medial collateral ligaments of the knee. Effect of treatment on stability and function of the joint.

We performed a retrospective study of sixty-six patients (forty-one male and twenty-five female) who had a combined injury of the anterior cruciate and medial collateral ligaments. Our purpose was to determine the prevalence of late valgus instability of the knee. The mean age of the patients was thirty-five years (range, sixteen to sixty-three years). The mean follow-up interval was forty-five months (range, twenty-one to 108 months). Twenty patients had been injured while snow-skiing; twenty-four, during other sports activities; seven, in a motor-vehicle accident; and the remaining fifteen, during activities of daily living. Eleven patients had reconstruction of the anterior cruciate ligament and repair of the medial collateral ligament, thirty-three had reconstruction of only the anterior cruciate ligament, and twenty-two were managed non-operatively. There was no evidence of valgus instability on clinical examination at the most recent follow-up visit. However, there was evidence of instability on stress roentgenograms of the knee in eight (13 per cent) of sixty patients. With the numbers available, we could detect no relationship between the presence of valgus instability and the method of treatment of the ligamentous tears (p > 0.4). We also compared the results for twenty-one of the thirty-three patients who had a combined ligamentous injury and reconstruction of only the anterior cruciate ligament with those for thirty-seven patients who had reconstruction of an isolated tear of the anterior cruciate ligament. After a mean follow-up interval of thirty-five months (range, twenty-one to sixty-six months), there was no difference in the anterior displacement, impairment of function, level of participation in sports activities, results of the one-leg-hop for distance test, or strength as determined by testing on a Cybex machine. On the basis of the findings in this study, we believe that, when there is mild or moderate valgus instability, an injury of the medial collateral ligament does not need to be repaired when the anterior cruciate ligament is repaired after a combined ligamentous injury.