Jürgen Höher

Evaluation and Treatment of Posterior Cruciate Ligament Injuries

Improved basic science data on the anatomy and bio-mechanics of the human posterior cruciate ligament have provided the orthopaedic surgeon with new information on which to base treatment decisions. Injuries to the posterior cruciate ligament are reported to comprise approximately 3% of all knee ligament injuries in the general population and as high as 37% in an emergency department setting. While the diagnosis of a posterior cruciate ligament injury can often be made with a physical examination, ancillary studies such as radiographs and magnetic resonance images can be very helpful in detecting associated ligament and bony injuries. In general, most partial (grades I and II) posterior cruciate ligament injuries can be treated nonoperatively. However, surgical reconstruction is usually recommended for those posterior cruciate ligament injuries that occur in combination with other structures. In this review, current surgical techniques of posterior cruciate ligament reconstruction based on anatomic and biomechanical studies will be discussed.

Biomechanical Analysis of a Posterior Cruciate Ligament Reconstruction Deficiency of the Posterolateral Structures as a Cause of Graft Failure

We hypothesized that posterior cruciate ligament reconstructions are often compromised by associated injuries to the posterolateral structures. Therefore, we evaluated a posterior cruciate ligament reconstruction in isolated and combined injury models using a robotic/ universal force-moment sensor testing system. The resulting knee kinematics and the in situ forces in the native and reconstructed posterior cruciate ligament were determined under four external loading conditions. In the isolated injury model, reconstruction reduced posterior tibial translation to within 1.5 1.3 to 2.4 1.4 mm of the intact knee at 30° and 90° under a 134-N posterior tibial load. In the combined injury model, deficiency of the posterolateral structures increased posterior tibial translation of the reconstructed knee by 6.0 2.7 mm at 30° and 4.6 1.5 mm at 90° of flexion. External rotation increased up to 14° while varus rotation increased up to 7°. In situ forces in the posterior cruciate ligament graft also increased significantly (by 22% to 150%) for all loading conditions. Our results demonstrate that a graft that restores knee kinematics for an isolated posterior cruciate ligament deficiency is rendered ineffective and may be overloaded if the posterolateral structures are deficient. Therefore, surgical reconstruction of both structures is recommended in the setting of a combined injury.

Hamstring graft motion in the femoral bone tunnel when using titanium button/ polyester tape fixation

Abstract The objective of this study was to determine the relative motion of a quadruple hamstring graft within the femoral bone tunnel (graft-tunnel motion) under tensile loading. Six graft constructs were prepared from the semitendinosus and gracilis tendons of human cadavers and were fixed with a titanium button and polyester tape within a bone tunnel in a cadaveric femur. Three different lengths of polyester tape (15, 25, and 35 mm loops) were evaluated. The femur was held stationary and uniaxial tensile loads were applied to the distal end of the graft using a materials testing machine. Each construct was subjected to loading for ten cycles with upper limits of 50 N, 100 N, 200 N and 300 N. Graft-tunnel motion was then determined using the distances between reflective tape markers placed on the hamstring graft and at the entrance to the femoral bone tunnel, which were tracked with a high-resolution video system. Graft-tunnel motion was found to range from 0.7 ± 0.2 mm to 3.3 ± 0.2 mm, and significant increases in graft-tunnel motion were observed with increasing tensile loads (P < 0.05). Shorter tape length (15 mm) resulted in significantly less motion when compared to longer tape length (35 mm) (P < 0.05). We conclude that graft-tunnel motion is significant and should be considered when using this fixation technique. Early stress on the graft, as seen in postoperative rehabilitation exercises and athletic activities, may cause large graft-tunnel motion before graft incorporation is complete. A shorter distance between the tendon tissue and the titanium button is recommended to minimize the amount of graft-tunnel motion. Alternative fixation materials to polyester tape, or different fixation techniques, need to be developed such that graft-tunnel motion can be reduced. Further studies are needed to evaluate the effect of graft-tunnel motion on graft incorporation in the bone tunnel.

The Effects of a Popliteus Muscle Load on In Situ Forces in the Posterior Cruciate Ligament and on Knee Kinematics A Human Cadaveric Study

To investigate the effect of simulated contraction of the popliteus muscle on the in situ forces in the posterior cruciate ligament and on changes in knee kinematics, we studied 10 human cadaveric knees (donor age, 58 to 89 years) using a robotic manipulator/universal force moment sensor system. Under a 110-N posterior tibial load (simulated posterior drawer test), the kinematics of the intact knee and the in situ forces in the ligament were determined. The test was repeated with the addition of a 44-N load to the popliteus muscle. The posterior cruciate ligament was then sectioned and the knee was subjected to the same tests. The additional popliteus muscle load significantly reduced the in situ forces in the ligament by 9% to 36% at 90° and 30° of flexion, respectively. No significant effects on posterior tibial translation of the intact knee were found. However, in the ligament-deficient knee, posterior tibial translation was reduced by up to 36% of the translation caused by ligament transection. A coupled internal tibial rotation of 2° to 4° at 60° to 90° of knee flexion was observed in both the intact and ligament-deficient knees when the popliteus muscle load was added. Our results indicate that the popliteus muscle shares the function of the posterior cruciate ligament in resisting posterior tibial loads and can contribute to knee stability when the ligament is absent.

Effects of sectioning the posterolateral structures on knee kinematics and in situ forces in the posterior cruciate ligament

Abstract The objective of this study was to determine the effects of sectioning the posterolateral structures (PLS) on knee kinematics and in situ forces in the posterior cruciate ligament (PCL) in response to external and simulated muscle loads. Ten human cadaveric knees were tested using a robotic/universal force-moment sensor testing system. The knees were subjected to three loading conditions: (a) 134-N posterior tibial load, (b) 5-Nm external tibial torque, and (c) isolated hamstring load (40 N biceps/40 N semimembranosus). The knee kinematics and in situ forces in the PCL for the intact and PLS-deficient knee conditions were determined at full extension, 30°, 60°, 90°, and 120° of knee flexion. Under posterior tibial loading posterior tibial translation with PLS deficiency increased significantly at all flexion angles by 5.5 ± 1.5 mm to 0.8 ± 1.2 mm at full extension and 90°, respectively. The corresponding in situ forces in the PCL increased by 17–¶19 N at full extension and 30° of knee flexion. Under the external tibial torque, external tibial rotation increased significantly with PLS deficiency by 15.1 ± 1.6° at 30° of flexion to 7.7 ± 3.5° at 90°, with the in situ forces in the PCL increasing by 15–90 N. The largest increase occurred at 60° to 120° of knee flexion, representing forces two to six times of those in the intact knee. Under the simulated hamstring load, posterior tibial translation and external tibial and varus rotations also increased significantly at all knee flexion angles with PLS deficiency, but this was not so for the in situ forces in the PCL. Our data suggest that injuries to the PLS put the PCL and other soft tissue structures at increased risk of injury due to increased knee motion and the elevated in situ forces in the PCL.

Graft choice and graft fixation in PCL reconstruction.

Several grafts and several fixation techniques have been introduced for PCL reconstruction over the past years. To date, autograft and allograft tissues are recommended for PCL reconstruction, whilst synthetic grafts should be avoided. Autograft tissues include the bone-patellar tendon-bone graft, the hamstrings and the quadriceps tendon. Allograft tissues are increasingly being used for primary PCL reconstruction. The use of allograft tissues requires a number of formal prerequisites to be fulfilled. Besides the previous mentioned graft types allograft tissues include Achilles and tibialis anterior/posterior tendons. To date no superior graft type has been identified. Several techniques and devices have been used for fixation of a PCL replacement graft. Most of these were originally developed for ACL reconstruction and then adapted to PCL reconstruction. However, biomechanical requirements of the PCL differ substantially from those of the ACL. To date, requirements for PCL graft fixations are not known. From a systematic approach femoral graft fixation can either be achieved within the bone tunnel (nearly anatomic) with an interference screw or outside the bone tunnel on the medial femoral condyle using a staple, an endobutton or a screw. Tibial graft fixation can be achieved either with an interference screw in the bone tunnel or with a staple, screw/washer or sutures tied over a bone bridge outside the bone tunnel (extra-anatomic). An alternative fixation on the tibial side is the inlay technique that reduces the acute angulation of the graft at the posterior aspect of the tibia. Further research is necessary to identify the differences between the various fixation techniques.

The Position of the Tibia during Graft Fixation Affects Knee Kinematics and Graft Forces for Anterior Cruciate Ligament Reconstruction

Ten cadaveric knees (donor ages, 36 to 66 years) were tested at full extension, 15°, 30°, and 90° of flexion under a 134-N anterior tibial load. In each knee, the kinematics as well as in situ force in the graft were compared when the graft was fixed with the tibia in four different positions: full knee extension while the surgeon applied a posterior tibial load (Position 1), 30° of flexion with the tibia at the neutral position of the intact knee (Position 2), 30° of flexion with a 67-N posterior tibial load (Position 3), and 30° of flexion with a 134-N posterior tibial load (Position 4). For Positions 1 and 2, the anterior tibial translation and the in situ forces were up to 60% greater and 36% smaller, respectively, than that of the intact knee. For Position 3, knee kinematics and in situ forces were closest to those observed in the intact knee. For Position 4, anterior tibial translation was significantly decreased by up to 2 mm and the in situ force increased up to 31 N. These results suggest that the position of the tibia during graft fixation is an important consideration for the biomechanical performance of an anterior cruciate ligament-reconstructed knee.

Viskoplastische Elongation eines gevierfachten Semitendinosussehnenkonstrukts mit Tape- und Fadenfixierung unter zyklischer Belastung

Die gevierfachte Semitendinosussehne wird von einigen Autoren als gleichwertiger Ersatz zum Patellarsehnentransplantat zur Rekonstruktion des vorderen Kreuzbands empfohlen. Einige klinische Fehlschläge mit diesem Transplantat veranlaßten uns, das primäre Transplantatkonstrukt biomechanisch zu untersuchen. Es war unsere Hypothese, daß infolge repetitiver, zyklischer Belastung eine viskoplastische Längenzunahme im Transplantatkonstrukt auftritt. 8 Semitendinussehnen von Leichengeweben wurden in der klinisch angewandten Technik zu einem Vierfachtransplantat präpariert. Zur proximalen Verankerung dienten ein Polyesterband und ein Titanplättchen. Die freien Sehnenenden wurden zur späteren distalen Fixierung mit Fäden um eine kortikale Fixierungsschraube angeschlungen. Das Titanplättchen und eine distale Kortikalisschraube wurden fest mit einer mechanischen Prüfmaschine zur weiteren Testung verbunden. Der Abstand der Fixierungspunkte lag bei 120 mm. Nach Präkonditionierung erfolgte das Knoten der Fäden bei maximaler Spannung. Es erfolgte zunächst eine Serie aus 5 zyklischen Belastungtests zwischen 20 und 100N (Test A) oder 20 und 150N (Test B). Die Testfolge war A1-A2-B1-B2-A3 mit einer 1stündigen Entlastung der Konstrukte zur möglichen Rückbildung viskoelastischer Effekte. Nach jeder Entlastungphase erfolgte eine Längenmessung bei 3N Vorspannung. Während der zyklischen Belastung wurde mit einer digitalen Videoanalyse die relative Bewegung innerhalb von 3 Abschnitten des Konstrukts bestimmt. Abschließend erfolgte ein Zerreißtest. In Folge der zyklischen Belastung kam es zu einer durchschnittlichen viskoplastischen Längenzunahme der Transplantatkonstrukte von 3,9 ± 0,9 mm. Nur ca. 3% dieser Längenzunahme fanden im Bereich des Sehnengewebes statt. Alle Konstrukte versagten durch Zerreissen des Mersilenebands bei einer Maximallast von 416 ± 36N. Die Steifigkeit lag bei 32,4 ± 1,3N/mm. Die Ergebnisse stützen die Hypothese, daß eine beträchtliche viskoplastische Längenzunahme in den Transplantatkonstrukten infolge zyklischer Belastung auftritt. Ähnliche Belastungen können in den Transplantatkonstrukten bei Kniebelastungen in der frühen postoperativen Phase auftreten und Ursache für eine Auslockerung vor Einheilung in den Knochenkanal sein. Wir schließen aus unseren Ergebnissen, daß eine aggressive Rehabilitation bei Verwendung dieser Technik nicht empfohlen werden kann. Verbesserte Techniken und/ oder Materialien zur Verankerung der Semitendinosusessehnen sollten entwickelt werden, um das biomechanische Verhalten der Transplantatkonstrukte zu verbessern.The purpose of this study was to determine the viscoplastic deformation in a quadrupled semitendinosus graft construct using a titanium button/ tape and screw post/suture fixation technique in response to cyclic loading. Eight quadrupled grafts for replacement of the anterior cruciate ligament (ACL) were prepared from human cadaveric semitendinosus tendons. For fixation, a polyester tape attached to a titanium button and four #2 nonresorbable sutures attached to each of the four tendon ends tied around a post screw were used. The graft construct was mounted on an INSTRON testing machine, with the titanium button and the post screw rigidly fixed at a constant distance of 120 mm. Cyclic creep tests (with 100 cycles each) were performed (A) between 20 and 100 N and (B) between 20 and 150 N (Fig. 1). The test sequence was A1-A2-B1-B2-A3 with a rest period of 1 h between single tests for graft recovery. The length of the graft construct after each rest period was used to determine the permanent elongation. Relative length changes along the graft construct (proximal, central, distal) were determined using a video tracking device. Finally, a load-to-failure test was performed. Under all test conditions the maximum elongation of the graft construct increased from the first to the 100th cycle, ranging from 1.0 mm to 3.1 mm. While these so-called creep patterns were almost identical in A1 and A2, elongations under A3 were 3–4 mm higher than under A1 and A2, probably as a result of higher loads at B1 and B2. The permanent elongation of the graft constructs after completion of the test series was 3.9 ± 0.9 mm. Further analysis revealed that about 97% of this deformation occurred within the fixation materials and interfaces (distal and proximal section) and only about 3% within the tendon tissue (central section). The load-to-failure test revealed an ultimate load of 416 ± 36 N and a stiffness of 32.4 ± 1.3 N/mm. All constructs failed at the polyester tape. Our results indicate that repetitive cyclic loading at relatively low loads can result in substantial, permanent elongation of a quadrupled semitendinosus graft construct with endobutton/tape and suture/post screw fixation method. Similar loads may be experienced by the graft construct during early postoperative activities and be a cause of gradual failure before graft incorporation is complete. We conclude that aggressive postoperative rehabilitation be applied with caution when using this graft construct. Better fixation materials and/ or techniques should be developed to improve biomechanical behavior of the graft construct.

Conservative versus Operative Treatment

An anterior cruciate ligament (ACL) tear is a common injury and arises most frequently in athletes from a noncontact pivoting injury, typically by a change of direction or deceleration manoeuvre. The annual incidence in the United States is about 200,000 with at least 100,000 receiving arthroscopic reconstruction [2]. The frequency of a partial tear of the ACL ranges from 10 to 35 % which is reported to be symptomatic in 5–10 % of the cases [3, 24].

Transosseous Repair of Root Tears of the Lateral Meniscus: Operative Technique and Short-Term Clinical Follow-Up of 28 Patients

An avulsion of the posterior tibial insertion of the lateral meniscus occurs during rotational distortion of the knee and can be associated with a tear of the anterior cruciate ligament (ACL). We performed a follow-up of 28 patients who, following anatomical ACL reconstruction using the ipsilateral semitendinosus graft, underwent either transosseous repair of the posterior lateral meniscus root () or no intervention (). The meniscus root tears were classified as Forkel I lesions. All patients were examined 6 months after surgery and undertook scoring using International Knee Documentation Committee Score (IKDC). Comparing the repair group with the no repair group the subjective IKDC 6 months after surgery was 75,72% (±1,019) and 75,56 (±1,058). Regarding the objective IKDC 8 × A (57,1%) and 6 × B (42,9%) could be ascertained in the repair group whereas 6 × A (42,9%), 6 × B (42,9%), and 2 × C (14,3%) scoring could be ascertained in the no repair group. It remains unclear if surgery on type Forkel I PLMRT provides benefits compared to the nonsurgical procedures as in both groups stability might occur. The purpose of this article was to report the outcome of surgical repair of lateral meniscus root tears.