Dietmar Urbach

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.

Characterisation of paired-pulse transcranial magnetic stimulation conditions yielding intracortical inhibition or I-wave facilitation using a threshold-hunting paradigm.

Abstract Short-interval, paired-pulse transcranial magnetic stimulation (TMS) is usually used to demonstrate intracortical inhibition. It was shown recently that with short-interval, paired-pulse TMS a facilitation – called intracortical I-wave facilitation – can also be demonstrated. It was the aim of this study to investigate which stimulus conditions lead to intracortical inhibition and what conditions yield an intracortical I-wave facilitation in a hand muscle of normal subjects. Paired-pulse TMS responses with an interstimulus interval of 1.2 ms were obtained from the abductor digiti minimi muscle of four normal subjects. A threshold-hunting paradigm with hunting through first or second stimulus variation was used to obtain a curve of threshold-pair strengths. All subjects showed two branches of stimulus interaction on this diagram. If the first stimulus of a threshold pair was below approximately 65% of resting motor threshold it modified the response primarily due to the second stimulus through intracortical inhibition. However, if the first stimulus of a threshold pair exceeded approximately 65% of resting motor threshold it became responsible for the spinal action-potential initiation. The subsequent second stimulus served as a ”booster” for the ongoing intracortical I-wave activity, making it impossible to observe the intracortical inhibition evoked by the first stimulus.

Effect of transcranial magnetic stimulation on voluntary activation in patients with quadriceps weakness

Joint disease causes weakness and wasting of adjacent muscles, in part because of inability to fully activate these muscles voluntarily. Previous findings suggest that transcranial magnetic stimulation (TMS) paired with muscle contractions enhances maximal voluntary contraction force (MVC) in healthy subjects by improving voluntary activation (VA). The aim of the present study was to evaluate whether such an effect is also present in subjects suffering from diminished muscle force due to decreased VA. Three single TMS over resting motor threshold were applied in 10 patients with a mean age of 62 years after total‐knee arthroplasty either during MVC or during muscle relaxation (control experiment) in a blinded randomized crossover study. MVC and VA were determined using a twitch‐interpolation technique at 1, 15, 30, and 60 min after stimulation. There was a significant effect of TMS on MVC if applied in synchrony with muscle contraction, and this persisted for at least 60 min beyond stimulation. In patients suffering from joint disease, TMS might make physiotherapy more effective. Muscle Nerve, 2005

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 transcranial magnetic stimulation on results of the twitch interpolation technique.

To investigate whether transcranial magnetic stimulation (TMS) has an effect on isometric muscle force elicited by maximal voluntary contractions (MVC) and the ability to activate a muscle voluntarily (VA, as a percentage of full muscle activation), a twitch‐interpolation technique was applied on the quadriceps femoris muscles of six volunteers before and within 1 min after TMS. VA improved by 5% (P = 0.019) and MVC by 17% (P = 0.002), whereas these parameters were unchanged in a control experiment. The results suggest that TMS has an effect on the central motor drive, at least within 1 min after stimulation.

Long-term Results After Arthroscopic Treatment of Synovial Chondromatosis of the Shoulder

PURPOSE The purpose of this study was to document the results of arthroscopic treatment for synovial chondromatosis of the shoulder with loose body removal and partial synovectomy. METHODS Five cases of shoulder arthroscopy performed for synovial chondromatosis were reviewed. Removal of loose bodies and partial synovectomy was performed in all cases. Follow-up of 4 to 9 years was obtained on these 5 patients. RESULTS The clinical result was very good for all patients. Radiologic signs of chondroma were observed in two patients. Revision surgery was not necessary in either case. CONCLUSIONS The clinical results referring to the Constant and Murley score and subjective assessment were very good at 4 to 9 years following surgery. However, in two out of five subjects, radiographs revealed evidence of persisting or recurrent synovial chondroma at follow-up. LEVEL OF EVIDENCE Level IV, therapeutic case series.

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.

Stimulus strength related effect of transcranial magnetic stimulation on maximal voluntary contraction force of human quadriceps femoris muscle

Abstract. It is well accepted that transcranial magnetic stimulation (TMS) can modulate motor cortex excitability long after application. Furthermore, a positive TMS effect on the ability to perform a maximal voluntary contraction (MVC) of the quadriceps femoris muscle has been described. However, stimulus strength dependence and duration of this effect are currently unknown. In the present study these parameters of the TMS-induced MVC enhancement were investigated in seven healthy subjects. Initially, three repetitive transcranial magnetic stimuli of varying stimulus strength were applied every 4 s either during MVC or relaxation. Thereafter, MVC and the ability to activate the quadriceps muscle voluntarily (voluntary activation) were determined using a sensitive twitch interpolation technique. In a second experiment we investigated the effect of three transcranial magnetic stimuli applied either during MVC or during relaxation on MVC over a time period of 30 min. There was a small but significant and stimulus strength related positive effect of TMS on MVC. The effect of TMS on voluntary activation was not significant. TMS had to be given during MVC to be effective and the positive effect of TMS when applied during MVC was still present after 30 min. These results indicate that TMS acts differently on the motor cortex depending on its activation status. TMS might have potential therapeutic applications in diseases associated with diminished cortical motor drive and subsequent muscle weakness.