Long-term effects of doping with anabolic steroids during adolescence on physical and mental health.

BACKGROUND: Systematic doping programs like in the GDR were applied in adolescent competitive athletes to induce supramaximal athletic performance. The substances had adverse somatic and psychological effects. The psychological development of the young athletes was impaired and they suffered in adulthood from long-term effects and secondary diseases even years after the doping period. METHOD: The study compared three groups: competitive athletes with doping (I), competitive athletes without doping (II) and persons with no sports activities (III). Somatic and psychological diseases were analyzed to identify the adverse effects of doping in the most vulnerable phase of development in adolescence. Participants were asked to supply a patient history and completed a questionnaire with standardized psychological tests. RESULTS: The doping cohort had a higher rate of somatic diseases, psychological disorders and social and professional difficulties. The differences were gender-specific with males more often having impaired liver function, depression, tumors and difficulties associated with the workplace . The doping group reported more emotional and physical neglect during childhood. They proved to be less optimistic but more pessimistic, to perceive less social support and to be more depressive. The study identified less extraversion and more neuroticism. Posttraumatic stress disorder (PTSD) occurred in a small number of participants in the doping group. Doping is associated with psychiatric variables. Predictors were the subscale identifying feelings of the Toronto alexithymia scale 20 (TAS-20), the sense of coherence and the Beck depression inventory 2 (BDI-II) and the Beck depression inventory (BDI). CONCLUSION: Physical and psychosocial effects imply correlation with the application of doping substances but might not only be due to the side effects of these substances but also caused by the system, which exerts great psychological pressure and stress during adolescence, a highly vulnerable phase.

Comparison of a minimally invasive procedure versus standard microscopic discotomy: a prospective randomised controlled clinical trial.

A Prospective randomised controlled study was done to determine statistical difference between the standard microsurgical discotomy (MC) and a minimally invasive microscopic procedure for disc prolapse surgery by comparing operation duration and clinical outcome. Additionally, the transferability of the results was determined by a bicentric design. The microscopic assisted percutaneous nucleotomy (MAPN) has been advocated as a minimally invasive tubular technique. Proponents have claimed that minimally invasive procedures reduce postoperative pain and accelerate the recovery. In addition, there exist only a limited number of well-designed comparison studies comparing standard microdiscotomy to a tubular minimally invasive technique that support this claim. Furthermore, there are no well-designed studies looking at the transferability of those results and possible learning curve phenomena. We studied 100 patients, who were planned for disc prolapse surgery at two centres [50 patients at the developing centre (index) and 50 patients at the less experienced (transfer) centre]. The randomisation was done separately for each centre, employing a block-randomisation procedure with respect to age and preoperative Oswestry score. Operation duration was chosen as a primary outcome parameter as there was a distinguished shortening observed in a preliminary study at the index centre enabling a sound case number estimation. The following data were compared between the two groups and the centres with a 12-month follow-up: surgical times (operation duration and approach duration), the clinical results, leg and back pain by visual analogue scale, the Oswestry disability index, length of hospital stay, return to work time, and complications. The operation duration was statistically identical for MC (57.8 +/- 20.2 min) at the index centre and for MAPN (50.3 +/- 18.3 min) and MC (54.7 +/- 18.1 min) at the transfer centre. The operation duration was only significantly shorter for the MAPN technique at the index centre with 33.3 min (SD 12.1 min). There was a huge clinical improvement for all patients regardless of centre or method revealed by a repeated measures ANOVA for all follow-up visits Separate post hoc ANOVAs for each centre revealed that there was a significant time-method (MAPN vs. MC) interaction at the index centre (F = 3.75, P = 0.006), whereas this crucial interaction was not present at the transfer centre (F = 0.5, P = 0.7). These results suggest a slightly faster clinical recovery for the MAPN patients only at the index centre. This was due to a greater reduction in VAS score for back pain at discharge, 8-week and 6-month follow up (P < 0.002). The Oswestry-disability scores reached a significant improvement compared to the initial values extending over the complete follow-up at both centres for both methods without revealing any differences for the two methods in either centre. There was no difference regarding complications. The results demonstrate that a shorter operation duration and concomitant quicker recovery is comprehensible at an experienced minimally invasively operating centre. These advantages could not be found at the transfer centre within 25 minimally invasive procedures. In conclusion both procedures show equal mid term clinical results and the same complication rate even if the suggested advantages for the minimally invasive procedure could not be confirmed for the transfer centre within the framework of this study.

Central motor deficits of the deltoid muscle in patients with chronic rotator cuff tears.

PURPOSE OF THE STUDY: Previous surface EMG studies have shown that chronic rotator cuff tears (RCT) may be associated with a altered activation of adjacent shoulder muscles. The effect of RCT on central neuromuscular control mechanisms of the shoulder girdle muscles such as the deltoideus muscle (MD), a key muscle of shoulder function, has as yet not been studied in detail. This study investigated the cortico-spinal excitability of the MD to assess the effects of RCT on the central neuromuscular function of upper limb muscles. MATERIAL AND METHODS: The motor evoked potentials (MEP) in response to transcranial magnetic stimulation of MD and first dorsal interosseus muscle (FDI) on both sides were obtained of six right-handed men with chronic, symptomatic, full-thickness RCT on the dominant sides. Stimulus response curves at four different levels were measured at two tasks (MD at rest and during activity). RESULTS: Different interactions were found between stimulus intensity, task and side for MEP of the MD (F = 3.9, P = 0.03), indicating that MD excitability on the affected side were lower when compared with the non-affected side. No correlation was found between the correspondent MEP amplitudes of MD and FDI at rest (r = 0.1, P = 0.44) and MD activation (r = 0.3, P = 0.05) on the affected side whereas a correlation existed on the non-affected side at rest (r = 0.5, P = 0.007) and during activation (r = 0.8, P < 0.001). CONCLUSIONS: These decreased cortico-motoneuronal excitability of the MD on the affected side seems to related to adaptive chan- ges in motor cortex as a consequence of chronic RCT. The data suggest an involvement of central mechanisms and seem to precede severe changes of osteoarthritis of the shoulder.

The patient-rated wrist evaluation (PRWE): cross-cultural adaptation into German and evaluation of its psychometric properties.

OBJECTIVE: To cross-culturally adapt the Patient-Rated Wrist Evaluation form (PRWE) into German (PRWE-G) and to evaluate its reliability and validity. METHODS: A cross-cultural adaptation of the PRWE was carried out, according to established guidelines. 103 patients, who had undergone resection interposition arthroplasty (RIAP) for carpometacarpal osteoarthritis approximately 6.2 years earlier, completed a questionnaire booklet containing the PRWE-G, the Short Form 36 (SF-36), the Disabilities of Arm, Shoulder, and Hand (DASH); they also underwent clinical assessment with the Hand Function Index (HFI, Keitel) and Custom Score including grip and pinch strength tests. The results were used to assess the criterion and construct validity of the PRWE-G. To measure the re-test reliability, 51 patients completed a second PRWE-G within 2 weeks. RESULTS: The test-retest reliability of the PRWE-G was acceptable for the pain and function sub-scales and for the global score, with intraclass correlation coefficients of 0.78-0.87. The PRWE-G showed a high internal consistency (Cronbach's alphas of 0.92-0.97 for the scales and the total score). The typical error of measurement for the global score was 8.1 points, giving a minimal detectable change (MDC95%) of approximately 22.5 points. The PRWE-G scores correlated well with those of the DASH (r=0.82, p<0.001) but less well with those of the physical component summary of the SF-36 (r=0.53, p<0.001) and not at all with the mental component summary scores of the SF-36 (r=0.04, p>0.05). The PRWE-G scores correlated moderately with certain clinical findings of the HFI, Custom Score, and grip/pinch strength tests (r=0.30-0.59, p<0.001). CONCLUSION: The PRWE-G represents a valid and reliable instrument to evaluate self-rated outcome in German-speaking patients with hand and wrist pathology.

The effect of irrigation time and type of irrigation fluid on cartilage surface friction.

It is known that fluid irrigation used during arthroscopic procedures causes a wash-out of lubricating substances from the articular cartilage surface and leads to increased friction. It was the goal of this study to investigate whether this effect depends on the time of irrigation and type of fluid used. Rabbit hind legs were used for the tests. The knees were dissected and the friction coefficient of the femoral cartilage measured against glass in a boundary lubrication state. To determine the influence of irrigation time and fluid, groups of 12 knees received either no irrigation (control), 15, 60 or 120min of irrigation with lactated Ringer's solution or 60min of irrigation with normal saline or a sorbitol/mannitol solution. The time of irrigation had a significant effect on the static and kinetic coefficient of friction (CoF), as had the type of fluid. Longer irrigation time with Ringer's solution was associated with increased friction coefficients (relative increase of the kinetic CoF compared to the control after 15, 60 and 120min: 16%, 76% and 88% respectively). The sorbitol/mannitol solution affected the static and kinetic CoF significantly less than either Ringer's or normal saline. The washout of lubricating glycoproteins from the cartilage surface and the associated increase of friction can be effectively influenced by controlling the time of irrigation and type of fluid used. The time of exposure to the irrigation fluid should be as short as possible and monosaccharide solutions might offer a benefit compared to salt solutions in terms of the resultant friction.

Ceramic prosthesis surfaces induce an inflammatory cell response and fibrotic tissue changes.

Aims: Early evidence has emerged suggesting that ceramic-on-ceramic articulations induce a different tissue reaction to ceramic-on-polyethylene and metal-on-metal bearings. Therefore, the aim of this study was to investigate the tissue reaction and cellular response to ceramic total hip arthroplasty (THA) materials in vitro, as well as the tissue reaction in capsular tissue after revision surgery of ceramic-on-ceramic THAs. Patients and Methods: We investigated tissue collected at revision surgery from nine ceramic-on-ceramic articulations. we compared our findings with tissue obtained from five metal-on-metal THA revisions, four ceramic-on-polyethylene THAs, and four primary osteoarthritis synovial membranes. The latter were analyzed to assess the amount of tissue fibrosis that might have been present at the time of implantation to enable evaluation, in relation to implantation time, of any subsequent response in the tissues. Results: There was a significant increase in tissue fibrosis with implantation time for all implant types tested. Interestingly, the tissue fibrosis in ceramic-on-ceramic THAs was significantly increased compared with metal-on-metal and ceramic-on-polyethylene. Additionally, we found ceramic wear particles in the periprosthetic tissue of ceramic implants. Fibroblasts responded with expression of cytokines when cultured on alumina-toughened zirconia (ATZ) and zirconia-toughened alumina (ZTA) ceramic surfaces. This response was more pronounced on ATZ ceramics compared with ZTA ceramics. The same inflammatory response was observed with peripheral blood mononuclear cells (PBMCs) cultured on ZTA and ATZ. Conclusion: Our findings therefore, corroborate the previous findings that ceramic-on-ceramic periprosthetic revision tissue is fibrous and offer an explanation for this observation. We detected a long-term inflammatory response of PBMCs and an inflammatory response of fibroblasts to ATZ and ZTA ceramic. These findings partially explain the fibrotic tissue change in periprosthetic tissue of ceramic-on-ceramic bearings. Cite this article: Bone Joint J 2018;100-B:882-90.

[The Effect of Intraoperative Screw Monitoring (Root Monitoring) with the INS-1 System (NUVASIVE) on the Radiological Outcome of Dorsal Instrumentation of the Lumbar Spine]. / Der Einfluss des intraoperativen Nervenwurzelmonitorings mit dem INS-1-System (NuVasive) auf das radiologische Outcome bei dorsaler transpedikulärer Instrumentation der Lendenwirbelsäule.

INTRODUCTION: Transpedicular screw fixation of spinal segments has been described for a variety of surgical indications and is a key element in spinal surgery. The aim of transpedicular screw fixation is to achieve maximal stability. Screw malposition should be obviated to avoid neurological complications. There are published methods of applying evoked EMG to control screw position in relation to neural structures. These studies demonstrated that an intact bony pedicle wall acts as an electrical isolator between the screw and spinal nerve root. The aim of our study was to evaluate the impact of intraoperative pedicle screw monitoring on screw positioning. MATERIAL AND METHODS: We enrolled 22 patients in this prospective randomised study, who underwent spinal instrumentation after being split into two equal groups. In the first group, dorsal instrumentation was supplemented with intraoperative nerve root monitoring using the INS-1-System (NuVasive, San Diego USA). In the second group, screws were inserted without additional pedicle monitoring. All patients underwent monosegmental instrumentation with "free hand implanted" pedicle screws. 44 screws were inserted in each group. The screw position was evaluated postoperatively using CT scans. The position of the screws in relation to the pedicle was measured in three different planes: sagittal, axial and coronal. The accuracy of the screw position was described using the Berlemann classification system. Screw position is classified in three groups: type 1 correct screw position, type 2 encroachment on the inner cortical wall, type 3 pedicle cortical perforation. Screw angulation and secondary operative criteria were also evaluated. RESULTS: The use of neuromonitoring did not influence the distance between the centre of the screws and the pedicle wall. Distances only depended on the implantation side (right and left) and the height of implantation (caudal or cranial screw). Because of the low number of cases, no conclusion could be reached about the influence of root monitoring on the correct positioning of the screws. There was at least a non-significant trend towards more frequent perforation of the pedicle in the monitor group. In the present study, we showed that root monitoring had a significant effect on the scattering of transversal angles. These were increased compared to the control group. Otherwise, the implantation angle was not shown to depend on the use of neuromonitoring. Neuromonitoring did not influence blood loss or operative time. DISCUSSION: The data did not permit any conclusion as to whether this technique can minimise the frequency of pedicle screw malposition. The four coronal plane distances did not depend on the use of neuromonitoring. The inclination angle was also unaffected by neuromonitoring. The only parameter for which we found any effect was the transverse angle. The mean values were similar in both groups, but the variances were not equal. The effect of monitoring on the only parameter which could not be evaluated by fluoroscopy is thus rather unfavourable.

Articulating polymethylmethacrylate (PMMA) spacers may have an immunomodulating effect on synovial tissue.

AIMS: Tissue responses to debris formed by abrasion of polymethylmethacrylate (PMMA) spacers at two-stage revision arthroplasty for prosthetic joint infection are not well described. We hypothesised that PMMA debris induces immunomodulation in periprosthetic tissues. PATIENTS AND METHODS: Samples of tissue were taken during 35 two-stage revision arthroplasties (nine total hip and 26 total knee arthroplasties) in patients whose mean age was 67 years (44 to 85). Fourier transform infrared microscopy was used to confirm the presence of PMMA particles. Histomorphometry was performed using Sudan Red and Haematoxylin-Eosin staining. CD-68, CD-20, CD-11(c), CD-3 and IL-17 antibodies were used to immunophenotype the inflammatory cells. All slides were scored semi-quantitatively using the modified Willert scoring system. RESULTS: The mean CD-68 scores did not show any significant change during the six weeks between the stages. Perivascular and diffuse scores showed significant difference in CD-3, CD-20, CD-11(c) and IL-17. At the time of re-implantation, a shift in the pattern of the expression of dendritic cells towards a perivascular arrangement and towards the periphery of PMMA particles was observed. Positive microbiological cultures were found at the time of re-implantation in three patients. Five further revisions were required for other reasons. CONCLUSION: Our results represent a biological reaction of the synovial tissues to spacers with a less diffuse expression of dendritic cells and an increased expression of perivascular lymphocytes. The use of spacers in two-stage revision for infection probably induces an immunomodulation of synovial tissues. Cite this article: Bone Joint J 2016;98-B:1062-8.

The pedicled rectus femoris muscle flap for reconstruction of complicated abdominal wall defects.

AIM OF THE STUDY: Large or complicated abdominal wall defects caused by recurrent incisional hernias, infections or tumor resections often require the use of prosthetic mesh, local tissue transposition or even distant muscle flaps for proper reconstruction. Due to the sometimes discouraging results of meshes muscle flaps are an appreciated alternative. We followed up a series of cases to assess the value of the pedicled rectus femoris muscle flap. METHODS: Follow up time ranged from 6 months to 4 years. 12 cases of reconstruction of the abdominal wall using pedicled rectus femoris muscle flaps after tumor resections, recurrent incisional hernias, and infection are presented. Abdominal wall stability was examined clinically. The aesthetic and the functional results were assessed using a standardized questionnaire. The loss of torque in the quadriceps muscle was evaluated using a dynamometer. RESULTS: In all but one patients a stable abdominal wall could be reconstructed. We saw no major complications. The loss of true muscular capacity in the quadriceps muscle of the operated leg was 19% compared to the nonoperated leg, but was tolerated very well. CONCLUSION: The donor site morbidity is moderate. The flap provides an easy and save possibility to reconstruct the abdominal wall. The rectus femoris muscle flap should be considered as an alternative for abdominal wall reconstruction.

Particle characterisation and cytokine expression in failed small-diameter metal-on-metal total hip arthroplasties.

The peri-prosthetic tissue response to wear debris is complex and influenced by various factors including the size, area and number of particles. We hypothesised that the 'biologically active area' of all metal wear particles may predict the type of peri-prosthetic tissue response. Peri-prosthetic tissue was sampled from 21 patients undergoing revision of a small diameter metal-on-metal (MoM) total hip arthroplasty (THA) for aseptic loosening. An enzymatic protocol was used for tissue digestion and scanning electron microscope was used to characterise particles. Equivalent circle diameters and particle areas were calculated. Histomorphometric analyses were performed on all tissue specimens. Aspirates of synovial fluid were collected for analysis of the cytokine profile analysis, and compared with a control group of patients undergoing primary THA (n = 11) and revision of a failed ceramic-on-polyethylene arthroplasty (n = 6). The overall distribution of the size and area of the particles in both lymphocyte and non-lymphocyte-dominated responses were similar; however, the subgroup with lymphocyte-dominated peri-prosthetic tissue responses had a significantly larger total number of particles. 14 cytokines (interleukin (IL)-1ß, IL-2, IL-4, IL-5, IL-6, IL-10, IL-13, IL-17, interferon (IFN)-γ, and IFN-gamma-inducible protein 10), chemokines (macrophage inflammatory protein (MIP)-1α and MIP-1ß), and growth factors (granulocyte macrophage colony stimulating factor (GM-CSF) and platelet derived growth factor) were detected at significantly higher levels in patients with metal wear debris compared with the control group. Significantly higher levels for IL-1ß, IL-5, IL-10 and GM-CSF were found in the subgroup of tissues from failed MoM THAs with a lymphocyte-dominated peri-prosthetic response compared with those without this response. These results suggest that the 'biologically active area' predicts the type of peri-prosthetic tissue response. The cytokines IL-1ß, IL-5, IL-10, and GM-CSF are associated with lymphocyte-dominated tissue responses from failed small-diameter MoM THA.

The RIPP density estimate: an alternative method for the estimation of peri-stimulus spike density.

Cross-correlation between stimuli and neuronal discharges determines the peri-stimulus spike density. This density function is usually estimated by the peri-stimulus time histogram (PSTH). In this paper an alternative method for spike-density estimation is considered that employs estimation of the rate of an inhomogeneous Poisson process by Jth waiting times. This procedure is called the RIPP density estimate. It involves sorting the spike times for all trials and obtaining the Poisson rates for successive groups of spikes. By application of this procedure to simulated action-potential sequences from the leaky-integrator model subject to a realistic input, it is shown that the RIPP density estimate reveals much more information from a given set of spike train data than a PSTH. An application of the RIPP density estimate to experimental spike train data from a human hand muscle motoneuron subject to a low-threshold-afferent volley is also presented.

Spike train analysis.

Procedures for the analysis of stimulus-correlated spike train data are reviewed. All procedures considered attempt to extract excitability changes evoked by the stimulus at the neuron investigated. The methods covered range from rather simple methods that require very little computational effort (raw spike train displays; peri-stimulus-time histogram (PSTH)) to more sophisticated procedures that attempt to extract all information available in the recorded spike-train data.

Rapid on-line estimation of responses to transcranial magnetic and peripheral nerve electrical stimulation in single human motoneurons.

Cross-correlation experiments allow to obtain information about synaptic potentials in human motoneurons. However, recording cross-correlation responses of one motoneuron to transcranial magnetic and electrical peripheral nerve stimulation requires a considerable recording time when both responses are recorded consecutively. In this paper a method is introduced yielding the same information about the responses of a single motoneuron to both types of stimuli while requiring only a fraction of the recording time necessary for a conventional cross-correlation experiment. The main features of the method introduced were: (i) use of the recharging time of the magnetic stimulator for response recording to the electrical stimulus, (ii) use of specific stimulus timing with respect to the motor unit discharges, and (iii) on-line display with statistical testing of the response functions allowing to stop stimulus application, if the responses to both types of stimuli had reached statistical significance. Application of the method is demonstrated with response recording of 70 tibialis anterior motor units from five healthy volunteers to transcranial magnetic and peroneal nerve electrical stimulation.

Characterization of human joint proprioception by means of a threshold hunting paradigm.

A method has been developed to measure the proprioceptive performance of movement detection in human joints, with the threshold hunting paradigm commonly used in other sensory modalities. Methods applied in former studies regarding movement detection were very time consuming (hours), making them not applicable to patients. Using the threshold hunting paradigm, the subject changes the parameter value continuously around the threshold producing a threshold hunting curve, which itself might be valuable for investigation of movement detection performance. The method presented here, is very quick compared to other studies in this field, especially when velocity is hunted and the threshold values are very low. The threshold parameter value is stable since there is a control at any time over the subject's stimulus perception. Furthermore, a Monte Carlo simulation showed that hunting curves can clearly be distinguished from guessing. Also reliability is given. All these points allow to use the method to evaluate the proprioceptive performance of a single individual. Considering the results, the method described may be useful for basic and clinical investigations regarding the proprioceptive performance limits of movement detection aspects.

Subdivision of primary afferents from passive cat muscle spindles based on a single slow-adaptation parameter.

38 primary afferents originating from de-efferented cat tibialis anterior muscle spindles were investigated. Ramp-and-hold stretches of the host muscle were performed with a varying amount of muscle pre-stretch while recording the primary afferent discharges. From the discharge responses an interspike interval function was estimated. This revealed a slow adaptation during the hold phase of stretch which could be approximated quite well by a power function. The slow-adaptation power function exponent (SAE) was found to be rather independent of the amount of pre-stretch applied to the host muscle and grouped around a value characteristic for each afferent. These 'characteristic SAEs' showed a clearly bimodal distribution within the population of primaries studied. Moreover, the distribution around both modes was narrow enough to justify the subdivision of the primary afferents according to their characteristic SAE as either high-SAE (10 afferents; 26%) or low-SAE (28 afferents; 74%) afferents. The most likely explanation for this bimodality of slow-adaptation behavior in primary afferents is given by the assumption that the afferent discharge of the passive spindle is mainly provided from a branch innervating either the bag1 (for high-SAE units) or the bag2 and chain (for low-SAE units) intrafusal fibers.

Re-afferent effects of individual static and dynamic gamma-stimuli during maintained fusimotor stimulation.

The ability of maintained dynamic and static fusimotor stimulation to modulate the primary afferent response of the muscle spindle in the rhythm of gamma-stimulation was investigated using a highly sensitive method for modulation detection. The effect of 41 gamma-fibers (13 dynamic; 28 static) on 38 primary afferents obtained from the tibialis anterior muscle of the cat was studied. It was found that maintained stimulation of 10 out of the 13 dynamic (77%) and of 25 out of the 28 static (89%) gamma-fibers could evoke significant modulations of the primary afferent response in the rhythm of fusimotor stimulation at a minimum of one stimulation rate. Moreover, both static and dynamic gamma-stimulations could evoke significant primary afferent modulations almost over the entire range of stimulation rates studied (30-300 stimuli per second). These results show that both gamma-systems can modulate the primary afferent response in the rhythm of fusimotor stimulation over a wide range of stimulation rates; thus the central nervous system may be provided with re-afferent information about the effect of each individual gamma-motoneuron discharge. Some hypotheses for the internal spindle mechanism responsible for the afferent modulations are discussed.

Effects of the amplitude threshold on the separability of neuropathic and myopathic from normal EMG using parameters of the turns/amplitude analysis.

OBJECTIVE: In this study, the relationship between the amplitude threshold used for the determination of the turns of the electromyographic (EMG) interference pattern and the parameters of the turns/amplitude analysis was examined. It was investigated whether the discrimination of myopathic and neuropathic from normal muscles could be optimized by an appropriate amplitude threshold. METHODS: The interference patterns of the tibialis anterior muscle of 15 patients with myopathies, 30 patients with neuropathies and 56 controls were recorded, using concentric needle electrodes. A computer program performed the Willison analysis, systematically varying the amplitude threshold between 10 microV and 200 microV. RESULTS: Amplitudes as well as the number of turns per second were non-linearly related to the amplitude threshold. The reduction of the amplitude threshold to 30 microV resulted in a clearly better separation of the distributions of the number of turns of neuropathic, myopathic and normal EMG, compared to the traditional threshold value of 100 microV. The distributions of amplitude values, however, were not affected. The distance between the turns parameter distributions of neuropathic patients and controls and between the distributions of myopathic patients and controls, expressed by the Kolmogoroff-Smirnov distance, had a maximum at 30 microV. CONCLUSIONS: For the turns/amplitude analysis of the tibialis anterior muscle an amplitude threshold of 30 microV should be selected.

On the applicability of two different stimulation techniques for intra-operative peroneal nerve conduction testing.

Dysfunction of the peroneal nerve is an important complication of knee surgery. We compared two monitoring procedures of peroneal nerve function during a standardized operation, a closing wedge high tibial osteotomy. For two types of stimulation the evoked compound motor unit action potentials (CMAPs) were recorded on the tibialis anterior muscle. We used direct perineural electrical stimulation of the common peroneal nerve distal to the cuff (dCMAPs) after nerve identification in the surgical field. Additionally, magnetic stimulation of the sacral plexus proximal to the cuff (pCMAPs) was performed. It was found that dCMAPs were recorded during almost one hour of tourniquet time whereas the pCMAPs were blocked after 25-30 min in 9 out of 11 cases. On the other hand, the CMAP obtained after proximal stimulation exhibited a latency shift with tourniquet yielding an indicator of ischaemic changes present beneath and distal to the tourniquet cuff. In conclusion, different applicabilities of both stimulation techniques under tourniquet conditions were demonstrated.

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.

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.