Gracilis and semitendinosus moment arm decreased by fascial tissue release after hamstring harvesting surgery: a key parameter to understand the peak torque obtained to a shallow angle of the knee.

PURPOSE: Semitendinosus and gracilis muscles whose tendons are used in surgical reconstruction of the anterior cruciate ligament maintain their contractile ability, but the peak torque angle of hamstring muscles shifted to a shallow angle postoperatively. The goal was to quantify the influence of the myofascial structures on instantaneous moment arms of knee muscles to attempt explaining the above-mentioned post-surgical observations. METHODS: Hamstring harvesting procedures were performed by a senior orthopaedic surgeon on seven lower limbs from fresh-frozen specimens. Femoro-tibial kinematics and tendons excursion were simultaneously recorded at each step of the surgery. RESULTS: No significant difference was demonstrated for instantaneous moment arm of gracilis during anterior cruciate ligament surgery (84% of the maximum intact values; P ≥ 0.05). The first significant semitendinosus moment arm decrease was observed after tendon harvesting (61% of the maximum intact values; p ≤ 0.005). After hamstring harvesting, the maximum and minimum moment arm (both gracilis and semi tendinosus) shifted to a shallow angle and 90°, respectively. CONCLUSION: Moment arm modifications by paratenons and the loose connective tissue release are essential to understand the peak torque obtained to a shallow angle. LEVEL OF EVIDENCE: Basic science study, biomechanics.

Tendon and fascial structure contributions to knee muscle excursions and knee joint displacement.

BACKGROUND: Semitendinosus and gracilis muscles whose tendons are used in surgical reconstruction of the anterior cruciate ligament maintain their contractile ability, and a limited decrease of hamstring muscles force is observed postoperatively despite important changes. The goal was to quantify the influence of the myofascial structures on excursions and moment arms of knee muscles to attempt explaining the above-mentioned post-surgical observations. METHODS: Hamstring harvesting procedures were performed by a senior orthopaedic surgeon on seven lower limbs from fresh-frozen specimens. Femoro-tibial kinematics and tendons excursion were simultaneously recorded at each steps of the surgery. FINDINGS: No significant difference was demonstrated for excursions and moment arms after tenotomies and gracilis tendon harvesting (P≥0.05). The first significant semitendinosus excursion (P<1.17×10(-4)) and moment arm (P<6.88×10(-5)) decrease was observed after semitendinosus tendon harvesting (46% of the initial excursion). INTERPRETATION: Gracilis and semitendinosus myofascial pathway is crucial for force transmission towards the knee joint.

Objective evaluation of cervical spine mobility after surgery during free-living activity.

BACKGROUND: Evaluation of cervical spine mobility after surgery is mainly based on the measurement of the range of motion during imposed movements. It can thus be questionable if this assessment represents the mobility experienced during daily life. The goal of this study was to propose a new evaluation tool based on the monitoring of cervical spine movement during daily activities. METHODS: The detection of cervical movement and the determination of primary motion component (lateral bending, axial rotation or flexion-extension), using two inertial sensors, were first validated in laboratory settings. Fifteen patients who underwent a cervical arthrodesis and nine healthy control subjects were monitored during their daily activity for half a day. The frequency of cervical movement was quantified according to posture, i.e. static and walking periods. The amplitude and velocity of cervical movement were evaluated using the median and cumulative distribution function. FINDINGS: The movement detection and classification showed an excellent performance (sensitivity and specificity>94%). For the daily monitoring, the patients presented a movement frequency similar to controls, whereas the amplitude and velocity in patients were lower than in controls (P<0.05). The differences between patients and controls were larger for the velocity parameters (effect sizes>0.37 and >0.54 for static and walking periods respectively) than for the amplitude parameters. INTERPRETATION: Body-worn inertial sensors enable the quantitative evaluation of global cervical movement. The movement amplitude and velocity during free-living conditions can be used as objective parameters to evaluate the cervical spine mobility after treatment.

Arthrodesis of the wrist with bone autograft and Hoffmann external fixation.

We report a series of 29 cases of wrist arthrodesis using a radiometacarpal half-frame or triangular Hoffmann configuration, bone autograft, and relocation of a retinacular rectangular flap under the extensor tendons to prevent adhesions. No splint or plaster cast has been used. Early active motion of the fingers was encouraged. The average duration of follow-up was 4 years. Bone healing was obtained in 27 patients after 104 days on average. All patients regained full finger movements and rotation of the forearm. Nine patients were reassessed on average 7.2 years after the arthrodesis: the VAS for pain at rest was 2.4/10, the DASH score 33/100, the grip strength 75% of the contralateral side on average.

[Reconstruction of the knee anterior cruciate ligament: single or double bundle?]. / Reconstruction du ligament croisé antérieur du genou: simple ou double faisceau?

Anatomical and biomechanical studies have shown that the anterior cruciate ligament (ACL) consists of two distinct bundles, the anteromedial (AM) and posterolateral. Each bundle has its specific role during the motion of the knee. ACL reconstruction techniques have focused on the restauration of the anteroposterior stability by substituting the more isometric AM bundle. Although these ligamentoplasties provide overall good results, in the last ten years double-bundle ACL reconstruction techniques have been developed, to better replicate the ligament anatomy. Despite the growing number of published studies, including randomized controlled trials comparing single bundle and double bundle reconstructions, there is still a lack of evidence of any superiority of the double-bundle technique. Furthermore, many series are criticized for their poor assessement of rotational stability, using most of the time subjective pivot shift clinical testing. Among the methods available to measure tibial rotation, 3-D optoelectronic evaluation is an attractive tool and has been used in some studies reporting rotational mesurements after ACL single-bundle reconstruction. Our Department of Orthopaedics and Traumatology has been using double-bundle techniques for a few years. We conducted a preliminary prospective randomized study, in order to compare single and double-bundle techniques by clinical and optoelectronic evaluations.

[Changes in knee kinematics and quadriceps and hamstrings moment arms after high valgus and varus tibial "dome" osteotomy: An in vitro study]. / Modifications de la cinématique du genou et des bras de levier du quadriceps et des ischio-jambiers après ostéotomie tibiale haute "curviplane" de valgisation ou de varisation: étude in vitro.

PURPOSE OF THE STUDY: Analysis of the correction or over-correction of high valgus and varus tibial osteotomies is generally limited to the frontal plane. Most likely however, the deformation observed radiographically in the frontal plane is simply a one-dimensional expression of a more complex three-dimensional deformation. This might be one of the causes for certain failures after surgery and recurrent problems which are difficult to solve. We proposed using 3D electrogoniometric to measure of the effect of a "dome" osteotomy on patellar and femoro-tibial kinematics and the changes in the moment arms of the knee muscles. MATERIAL AND METHODS: We used five lower limbs harvested from non-fixed cadavers. A "dome" osteotomy was stabilized by external fixation. Three-dimensional analysis of the femoro-tibial and femoro-patellar kinematics was performed using two electrogoniometers with six degrees of freedom. Changes in the lengths of the hamstrings and quadriceps was measured using four LVDT linear variable differential transformers. The muscles lever arms were measured with the tendon excursion method. RESULTS: At 90 degrees flexion, varus osteotomy induced internal rotation while valgus osteotomy induced the opposite effect. Beyond 40 degrees flexion, there was a clear internal rotation of the patella for varus and neutral corrections. Valgus corrections however induced external rotation. The peak lever arm of the quadriceps increased with valgus, while the angle of the peak was higher for varus correction. Valgus appeared to increase the lever arm of the semitendinous. DISCUSSION: Our study demonstrated that the effect of tibial osteotomy is not limited to the frontal plane. Tibial rotations are observed systematically for all corrections in the frontal plane. Varus correction tends to create internal rotation while valgus correction tends to have the opposite effect. Axial correction also affects patellar kinematics. Interanal rotation is induced by varus correction and external rotation by valgus correction. This patellar rotation could result from tibial rotations induced by the different corrections. The loss of the parallelism between the patellar crest and the trochlear groove could produce changes in femoropatellar surface contact and pressure, potentially leading to pain or cartilage degeneration. The maximal value of the quadriceps moment arm appears to increase with valgus. The efficacy of the quadriceps could thus be improved with valgus, potentially increasing extension force. Valgus increases the moment arm, improving limb flexion, while varus correction has the opposite effect. This could explain a loss in flexion amplitude in patients with varus or who underwent varus osteotomy. Tibial osteotomy is designed to correct the deviation solely in the frontal plane but also has effects in all three planes. Further 3D analyses of the morphology and physiology of the knee joint would be needed to better understand the physiological and pathological processes involved.

The use of disharmonic motion curves in problems of the cervical spine.

Cervical spine motion was investigated by three-dimensional electrogoniometry in 257 asymptomatic volunteers and in 32 patients with cervical disc hernia or whiplash syndrome. Maximal ranges of main and coupled motions were considered. Motion curves were analysed qualitatively and using fitting of sixth degree polynomials. Motion ranges obtained were in agreement with previous observations. Significant differences between patients and volunteers concerned several primary and coupled components but not all. Qualitatively, patients displayed less harmonic curves, with irregularities and plateau-like appearances. Root mean square differences between data and fit were significantly modified in patients. Although cervical spine motion ranges may remain within normal limits in patients, motion patterns were altered qualitatively and quantitatively. Motion pattern analysis might prove a useful discrimination parameter in patients in whom anatomical lesions are not clearly identifiable.