Wolfgang Nebelung

Bilateral deficit of voluntary quadriceps muscle activation after unilateral ACL tear.

PURPOSE The inability to fully activate the quadriceps femoris muscle voluntarily is known to accompany several different knee-joint pathologies. The extent of a voluntary-activation deficit in patients after isolated rupture of the anterior cruciate ligament (ACL), however, has been reported to be small or nonexistent, making it questionable if a voluntary-activation deficit is a relevant factor for these patients at all. METHODS In this study the ability to voluntarily activate the quadriceps femoris muscles was quantified in 22 male patients with arthroscopically-proven isolated ACL ruptures using an established highly sensitive twitch-interpolation technique. Furthermore, the maximal voluntary contraction force of the quadriceps muscle was obtained by isometric knee-joint torque measurements. The results were compared with an age-, gender-, and activity-matched control group. RESULTS There was a moderate but significant mean reduction in maximal voluntary activation (VA) in both the injured (VA: 83.9 +/- 2.3%, mean +/- SEM) and uninjured side (VA: 84.7 +/- 2.2%) in comparison with controls (VA: 91.1 +/- 0.8%). However, of the patients the 23% who presented a considerably reduced voluntary-activation of less than 80% were mainly responsible for the significant mean deficit. CONCLUSIONS The deficit of isometric muscle strength on the injured side compared with that of controls was explained by the voluntary-activation deficit and a true muscle weakness. On the other hand, the diminished muscle strength of the uninjured side was explained sufficiently by the voluntary-activation deficit alone. Considering the bilateral voluntary-activation deficit, functional muscle tests might not be valid when the uninjured extremity serves as reference.

Effects of reconstruction of the anterior cruciate ligament on voluntary activation of quadriceps femoris: A PROSPECTIVE TWITCH INTERPOLATION STUDY

The loss of full muscle activation contributes to weakness of the quadriceps muscle in patients with deficiency of the anterior cruciate ligament (ACL). We examined whether a deficit of voluntary activation (VA) of the quadriceps muscle can be reversed by reconstruction of the ACL and assessed its influence on muscle strength and clinical parameters. We evaluated 12 male subjects with an isolated tear of the ACL and 12 matched control subjects before operation and two years after reconstruction of the ACL. Assessment included measurements of isometric knee-extension torque at maximal voluntary contraction (MVC force), knee stability tests, the International Knee Ligament Standard Evaluation Form and the Tegner activity score. A sensitive method of twitch interpolation was used to quantify the VA and to calculate true muscle force. Before operation we found a deficit of VA on both the injured (mean +/- SEM 74.9 +/- 3.5%) and the uninjured side (74.6 +/- 3.0%) in comparison with the control group (91 +/- 0.9%). Two years after reconstruction of the ACL the VA improved significantly on both sides but remained less than that of the controls. Correlation analysis revealed an improvement of the VA in patients who returned to a higher level of activity. The deficit of true muscle force, however, persisted regardless of the clinical outcome and ligament stability.

Detailed analysis of proprioception in normal and ACL-deficient knees

We assessed proprioception using threshold levels for the perception of knee movement at slow angular velocities (0.1 degrees/s to 0.85 degrees/s) in 20 patients with unilateral tears of the anterior cruciate ligament (ACL) and 15 age-related control subjects. Failure to detect movement was also analysed. The threshold levels of detection did not differ between the damaged and undamaged knees in the patients or between the patients and the control group. Failure to appreciate movement, however, was significantly greater in knees with ACL loss compared with the undamaged knees of patients and the control group. Our findings show a proprioceptive deficit in the absence of the ACL. Measurements of threshold levels of detection of passive movement alone are not suitable for the evaluation of proprioceptive loss in ACL deficiency; assessment of failure to appreciate movement is essential.

Biomechanical properties under cyclic loading of seven meniscus repair techniques

The purpose of the current study was to obtain additional information about the biomechanical behavior of different fixation techniques for meniscus repair using recently developed biodegradable implants and suture repair techniques. The posterior horns of human menisci were used to investigate the meniscus repair construct of the Arrow™, Screw™, Stinger™, Fastener™, T-fix™, and horizontal and vertical mattress suture. A 20 mm-longitudinal incision was made in the meniscus, similar to a bucket handle lesion, 3 mm from the meniscosynovial rim and was repaired. One hundred cycles between 5 N and 15 N were done using a tension load machine with a loading rate of 10 N/second. The stiffness, displacement, and pullout strength were examined. The significantly highest stiffness was found for the vertical mattress suture (17.1 N/mm) and Stinger (15 N/mm) followed by the Arrow (13.7 N/mm), T-fix (10.5 N/mm), and horizontal mattress suture (10 N/mm). Superior load to failure was obtained for the suture repair in comparison with the biodegradable implants. Despite the lower pullout strength of biodegradable implants, similar stiffnesses were found for the Stinger and Arrow in comparison with the mattress suture technique. These techniques provide the most rigid fixation that is essential for tissue healing.

IMMUNOHISTOCHEMICAL ANALYSIS OF SEVERAL PROTEOLYTIC ENZYMES AS PARAMETERS OF CARTILAGE DEGRADATION

Osteoarthritis is the most common joint disease in humans. It is characterized by a gradual loss of extracellular matrix components of articular cartilage such as collagen and proteoglycan. Presently, however, emphasis is placed on enzymes exerting a strong influence on cartilage degradation. These enzymes include matrix metalloproteinases (MMP), their specific inhibitors (TIMP) and the plasminogen activator/inhibitor system. We applied monoclonal antibodies against MMP-1, -2, -3, -9 and their inhibitors TIMP-1/-2, as well as against urokinase-plasminogen activator u-PA and its inhibitor PAI to investigate their influence on articular cartilage degradation in patients with varusgonarthritis. We examined the cartilage of the lateral and medial compartments of 20 tibia plateaus, which can present with slight and severe cartilage degradations at the same time. In doing so, we tried to show whether or not immunohistological detection of enzymes could serve as a parameter for chondral degradation. The strongest immunoreaction for all enzymes was noted in the superficial layer of articular cartilage both medially and laterally. Between medial and lateral compartments, however, there were striking differences in the immunoreaction intensity of chondrocytes for MMP-1 and -3 as well as for TIMP-1 and u-PA. We noted that in cartilage with more advanced degradation, the immunoreaction for these enzymes was significantly higher in medial than in lateral compartments (p < 0.05). At the immunohistological level, a direct correlation between the grade of cartilage degradation and immunoreaction intensity was found. Our results corroborate the assumption that the expression of certain matrix-degradating enzymes serves as a parameter for the grade of cartilage degradation.

Surgical Treatment of Isolated Patellofemoral Osteoarthritis

Isolated patellofemoral osteoarthritis in the healthy middle-aged population is a challenging problem. Fifty-one knees in 50 patients with isolated patellofemoral osteoarthritis were treated by partial lateral facetectomy, lateral release, and medialization of the tibial tubercle. The minimum followup was 7 months (mean, 20.2 months; range, 7–32 months). Preoperative radiographs showed Ahlbäck Grades III and IV lateral patellofemoral joint space narrowing. The mean age of the patients was 60.1 years (range, 46–81 years). The subjective outcome was based on the WOMAC and the McCarroll score. Posteroanterior flexion weightbearing views, lateral views, and 45° axial views were taken. According to the WOMAC score, the scores improved considerably by 2.34 points with respect to pain and by 1.63 points with respect to function. The Insall-Salvati index decreased considerably but still remained in the physiologic range. The majority of these patients experienced improvement in their patellofemoral symptoms. However, the clinical outcome was not better in comparison to other surgical procedures. After the short followup, we would not recommend combined lateral facetectomy, lateral release, and medialization of the tibial tubercle until longer results are available.Level of Evidence: Level IV Therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Structural Properties of Sutures Used in Anchoring Multistranded Hamstrings in Anterior Cruciate Ligament Reconstruction: A Biomechanical Study

Sutures are frequently used in anchoring hamstring or quadriceps tendon grafts in cruciate ligament reconstruction. Trumpet like widening of the femoral bone canal was found in patients having had anterior cruciate ligament reconstruction with hamstring autograft. We investigated 5-mm Polylene tape (Genzyme, Boston, MA) and Mersilene tape (Ethicon, Somerville, NJ) as well as No. 6 Ethibond sutures (Ethicon) for ultimate load, stiffness, and elongation under tension of 50 N, 150 N, 250 N, and ultimate load. The Mersilene and Polylene tapes were tested in single loops and Ethibond in double loops having a length of 30 mm. The length is similar to that used intraoperatively for the graft fixation. The suture materials were loaded using a material testing machine at a strain rate of 60 mm/min. The ultimate loads of the loops with knots were 474 N +/-24.7 N for Polylene, 437 N +/-38.2 N for Mersilene, and 338 N +/-16.8 N for Ethibond, and was statistically significant (analysis of variance [ANOVA], P<.05). The elongation under a tension load of 50 N was similar for Ethibond (1.2+/-0.216 mm) and Polylene (1.3+/-0.32 mm). Mersilene (1.7+/-0.34 mm) showed an increased elongation (ANOVA, P=.03). The stiffness for Ethibond was 37.1+/-2.7 N/mm, for Mersilene 38.4+/-3.8 N/mm, and for Polylene was 47+/-3.1 N/mm. The Polylene tape appears to be the most suitable material in terms of strength and stiffness. Nevertheless, the stiffness of all the tested materials is greatly inferior to the stiffness of the commonly used grafts. We believe that a stiffer graft construct might reduce motion during the early period of ingrowing.

Semitendinosussehne vs. Ligamentum patellae Klinische Ergebnisse einer prospektiven randomisierten Studie nach vorderer Kreuzbandplastik

ZusammenfassungDas Ziel der vorliegenden prospektiven randomisierten Studie ist die klinische Evaluation der 2-Jahres-Ergebnisse nach arthroskopischer Ersatzplastik des vorderen Kreuzbands unter Verwendung des mittleren Patellarsehnendrittels oder der Semitendinosussehne. Methodik. 20 Patienten wurden in arthroskopischer transtibialer Technik mit einem mittleren Patellarsehnentransplantat (BTB-Gruppe) mit 20 Patienten mit gedoppelter Semitendinosussehne (SET-Gruppe) postoperativ untersucht. Die klinische Evaluation erfolgte präoperativ und zum Zeitpunkt der Nachuntersuchung mittels IKDC, Tegner-Aktivitätslevel sowie dem retropatellare Schmerzscore nach McCarroll. Zur Bestimmung der a.-p.-Translation im Seitenvergleich diente der KT-1000. Ergebnisse. Bezüglich des Gesamtergebnisses im IKDC erreichten in der SET-Gruppe 80% und in der BTB-Gruppe 50% der Patienten gute oder sehr gute Ergebnisse. Die Differenz der a.-p.-Translation im Seitenvergleich betrug in der BTB-Gruppe 1,6 mm (−2–4 mm) und in der SET-Gruppe 2,7 mm (0–7mm) (p<0,05). Die retropatellaren Beschwerden waren im Mc Carrol-Score in der BTB-Gruppe (17,4 Punkte) ausgeprägter als in der SET-Gruppe (19,5 Punkte) (p<0,05). Hinsichtlich der Rückkehr zum früheren Aktivitätsniveau (Tegner-Score SET und BTB 6,9) erreichte die SET-Grupp 2 Jahre postoperativ 6,7 und die BTB-Gruppe 5,6 Punkte. Schlussfolgerung. Da die Kreuzbandplastik mittels gedoppelter Semitendinosussehne trotz geringerer Stabilität ein besseres Gesamtergebnis nach dem IKDC-Score zeigte, ist das Verfahren als Alternative anzusehen. Zur Verbesserung der Stabilität ist die Verwendung von 3- oder 4-fach-Transplantaten mit einer stabileren Fixation anzuraten.AbstractThe aim of our prospective randomised study was to evaluate the clinical results after arthroscopical reconstruction of the ACL using the midthird patellar ligament or semitendinosus tendon. Methods. Forty patients were followed up two years postoperatively. Twenty of them received either a patellar ligament graft (BTB-group) or doubled semiteninosus tendon (SET-group). The clinical evaluation included the preoperative and two years postoperative assessment, based on the IKDC-Score, Tegener-Score and Mc-Carroll-Score. The a.p.-translation was evaluated using the KT-1000. Results. Sixteen (80%) patients of the SET-group and 10 (50%) patients of the BTB-group showed good and excellent results in the over all assessment with the IKDC-Score. The mean side to side KT-1000 difference yielded 1.6 mm (−2–4 mm) in the BTB-group and 2.7 mm (0–7 mm) in the SET-group (p<0.05). The retropatellar pain syndrome based on the Mc-Carroll-Score showed 17.4 points in the BTB-group in comparison to 19.5 points in the SET-group (p<0.05). The level of activity using the Tegner-score showed preoperatively for both the SET- and BTB –group 6.9 points and postoperatively for the SET-group 6.7 points and for the BTB-group 5.6 points. Conclusions. Despite the inferior a.p.-stability for the patients who received doubled semitendinosus tendon grafts they presented clinically superior results compared to the BTB-group. Therefore this technique seems to be the alternative method. In order to improve the stability we recommend the usage of three or four stranded grafts and an improved fixation technique.

Bilateraler Funktionsverlust der Quadrizepsmuskulatur nach einseitiger Kreuzbandruptur mit Begleitverletzung durch zentrales Aktivierungsdefizit

ZusammenfassungZiel der Studie war es zu untersuchen, in welchem Ausmaß ein Defizit der willkürlichen Aktivierbarkeit des M. quadriceps bei schweren Knieverletzungen vorliegt und welchen Einfluss ein Aktivierungsdefizit auf die Muskelfunktion hat. Untersucht wurden 33 männliche Patienten nach Rupturen des vorderen Kreuzbandes (VKB) mit Begleitverletzungen der Kniegelenke im Vergleich zu 22 Patienten mit einer isolierten VKB-Ruptur und einem altersangepassten gesunden Kontrollkollektiv. Mit einer sensitiven Twitch-Interpolationsmethode wurde die isometrische Maximalkraft des M. quadriceps und die Fähigkeit der Probanden, die Quadrizepsmuskulatur willentlich zu aktivieren, bestimmt.Die Patienten mit VKB-Ruptur und Begleitverletzungen hatten eine signifikant schlechtere Aktivierbarkeit der Quadrizepsmuskulatur sowohl auf der verletzten (78,8±2,09%, mean±SEM) als auch gleichermaßen auf der gesunden Seite (78,9±1,91%) im Vergleich zu dem Kontrollkollektiv und zu der Gruppe mit isolierter VKB-Ruptur. Der gemessene Kraftverlust beruhte auf der gesunden Seite alleine auf das beschriebene Aktivierungsdefizit, der Kraftverlust der verletzten Seite dagegen auf das Aktivierungsdefizit und Muskelatrophie. Aktivierungsdefizite sind vermutlich eine Erklärung dafür, dass sich bei einigen Patienten trotz intensiver Therapie eine Muskelatrophie nicht verhindern lässt. Aufgrund bilateraler Aktivierungsdefizite muss die Validität von Muskelfunktionstest, die die gesunde Seite als Referenz nutzen, angezweifelt werden.AbstractThe aim of the study was to investigate the ability to activate the quadriceps femoris muscle voluntarily in patients after severe knee injuries and its influence on muscle function. 33 male patients after ACL-rupture with concomitant injuries were investigated with a twitch-interpolation-method to determine the maximal voluntary contraction force (MVC) and the ability to activate the quadriceps muscle voluntarily. The results were compared to a previously investigated group of patients after isolated ACL-rupture and to an aged-matched control group.The patients with extensive knee injuries presented a significant higher deficit of voluntary quadriceps muscle activation on the injured (78.8±2.09%, mean±SEM) and equally on the uninjured side (78.9±1.91%) compared to the patients after isolated ACL-rupture and to controls. A minor MVC-deficit of the patients quadriceps muscle of the uninjured side could be explained by the voluntary activation deficit alone, the major MVC deficit of the injured side by muscle atrophy and a voluntary activation deficit. The activation deficit is probably the underlying reason for persisting muscle wasting and weakness despite intensive physiotherapy especially in patients with concomitant injuries in addition to an ACL-rupture.

Effects of reconstruction of the anterior cruciate ligament on voluntary activation of quadriceps femoris

The loss of full muscle activation contributes to weakness of the quadriceps muscle in patients with deficiency of the anterior cruciate ligament (ACL). We examined whether a deficit of voluntary activation (VA) of the quadriceps muscle can be reversed by reconstruction of the ACL and assessed its influence on muscle strength and clinical parameters. We evaluated 12 male subjects with an isolated tear of the ACL and 12 matched control subjects before operation and two years after reconstruction of the ACL. Assessment included measurements of isometric knee-extension torque at maximal voluntary contraction (MVC force), knee stability tests, the International Knee Ligament Standard Evaluation Form and the Tegner activity score. A sensitive method of twitch interpolation was used to quantify the VA and to calculate true muscle force. Before operation we found a deficit of VA on both the injured (mean +/- SEM 74.9 +/- 3.5%) and the uninjured side (74.6 +/- 3.0%) in comparison with the control group (91 +/- 0.9%). Two years after reconstruction of the ACL the VA improved significantly on both sides but remained less than that of the controls. Correlation analysis revealed an improvement of the VA in patients who returned to a higher level of activity. The deficit of true muscle force, however, persisted regardless of the clinical outcome and ligament stability.