Repeated ankle sprains and delayed neuromuscular response: acceleration time parameters.

STUDY DESIGN: A comparative study. OBJECTIVES: To assess whether in subjects with unilateral chronic ankle instability the dynamic reaction time of the affected ankle differs from the healthy ankle and from ankles of a control group. BACKGROUND: Reaction time is an essential element in joint protection against sudden unexpected excessive movement requiring fast and coordinated muscle action. During a sudden ankle inversion movement, a reflex action of the evertor muscles is needed to counteract the movement. Adequate neuromuscular response is crucial and a delayed response could contribute to inversion trauma and subsequently to chronic ankle instability. The isokinetic dynamometer acceleration time (ACC-TIME) provides valuable information on dynamic neuromuscular ability. MATERIAL AND METHODS: Patients with unilateral chronic ankle instability (n = 11) and healthy individuals in a control group (n = 11) were tested on an isokinetic dynamometer during 3 sets of 3 reciprocal inversion/eversion movements of both ankles at 30 degrees/s and 120 degrees/s. Analysis of variance models were used to compare the ACC-TIME of the affected ankle to the unaffected ankle of the same subjects and a control group. RESULTS: For the evertor muscles at 30 degrees/s and 120 degrees/s a significantly prolonged ACC-TIME was found when comparing the affected ankles to the contralateral ankles and both ankles of the control group. For the invertor muscles at 120 degrees/s a significantly prolonged ACC-TIME was found when comparing the affected ankle to the unaffected ankles of patients and those of the control group. CONCLUSIONS: Because the most important evertor muscles are innervated by the fibular nerve, the significantly prolonged ACC-TIME of the affected ankle is consistent with the finding of a lower motor nerve conduction velocity of the fibular nerve after inversion trauma. The results support the concept of a delayed neuromuscular response as an important factor in the etiology of chronic ankle instability.

Relations between pregnancy-related low back pain, pelvic floor activity and pelvic floor dysfunction.

To assess the occurrence of pelvic floor dysfunction (PFD) in pregnancy- related low back and pelvic pain (PLBP) patients, a cross-sectional study was performed, comprising 77 subjects. Each subject underwent physical assessment, and filled in the Urogenital Distress Inventory completed with gynaecological questions. Differences in the presence of PFD between PLBP patients and healthy controls as well as differences in pelvic floor muscle activity were tested for significance. Interaction by age and vaginal delivery were tested. PFD occurred in 52% of all PLBP patients, significantly more than in the healthy control group. In PLBP patients a significantly increased activity of the pelvic floor muscles could be demonstrated with respect to healthy controls. The occurrence of PFD and PLBP was influenced by a confounding effect of age. Clinicians should be aware of the relation between PLBP and PFD and hence address both problems at the same time.

Contribution of pelvic floor muscles to stiffness of the pelvic ring.

STUDY DESIGN: A biomechanical study in embalmed specimens, on the relation between applied tension in the pelvic floor muscles, stiffness of the pelvic ring and generation of movement in the sacroiliac joints. OBJECTIVE: To gain insight into the effect of tension in the pelvic floor muscles on stiffness of the pelvic ring. Background. According to a model on selfbracing pelvic floor muscles have the capacity to stiffen the sacroiliac joints. However, this capacity has not been demonstrated in vitro yet. METHODS: In 18 embalmed specimens an incremental moment was applied to the sacroiliac joints to induce rotation of the innominate bones in the sagittal plane. After assessment of the relationship between rotation angle and moment, springs were applied to the pelvis to simulate tension in the pelvic floor muscles. During the simulated tension the measurements were repeated. Differences in stiffness before and after applying springs were tested for significance. RESULTS: In females, simulated tension in the pelvic floor muscles stiffened the sacroiliac joints with 8.5% (P < 0.05). In males no significant changes occurred. In both sexes a backward rotation of the sacrum occurred due to simulated tension in the pelvic floor muscles (P < 0.05). The sacroiliac joints of female specimens were more mobile in comparison to male specimens (P < 0.05). CONCLUSIONS: In females, pelvic floor muscles have the capacity to increase stiffness of the pelvic ring. In addition, these muscles can generate a backward rotation of the sacrum in both sexes. RELEVANCE: The ability of pelvic floor muscles to increase stiffness of the pelvic ring is of importance in patients with impairment of pelvic stability, especially in pelvic pain patients. Increased activity of these pelvic floor muscles might compensate for loss of pelvic stability by stiffening the pelvic ring and restoring proper load transfer through the lumbopelvic region.

The influence of slouching and lumbar support on iliolumbar ligaments, intervertebral discs and sacroiliac joints.

OBJECTIVE: To investigate lumbopelvic kinematics when moving into a slouch. DESIGN: A biomechanical model was developed. Load tests in vitro verified the model. BACKGROUND: The precise mechanism causing disc herniation and back sprain is still debated. Most biomechanical studies have focused on lifting in a stooped posture. Previous studies address instability situations due to Euler buckling of the spine under axial load. However, no studies address lumbosacral, iliolumbar and sacroiliac kinematics in slouching, i.e. flexing the spine in situations with negligible compressive spinal load. METHODS: Modeling started with the click-clack movement, i.e. the transition from lumbar lordosis to lumbar kyphosis by the combination of backward rotation of the pelvis and ventral flexion of the spine. The flexed spine was compared with a crowbar which uses the iliolumbar ligaments as fulcrum and pivot. To analyse the click-clack movement in sitting, unembalmed erect human trunks were moved from a forward position to a backward position, recording angular changes between L5, sacrum and ilium. RESULTS: When moving the trunk stepwise backward with support at shoulder level, L5 showed forward rotation with respect to the sacrum, but rotation of the sacrum with respect to the iliac bones was reversed (i.e. counternutation). L5 showed displacement in ventral direction with respect to the ilium. Measurements were in agreement with prediction from the crowbar model of the spine. CONCLUSIONS: Backward rotation of the pelvis combined with flexion of the spine, i.e. slouching, results in backward rotation of the sacrum with respect to the ilium, dorsal widening of the intervertebral disc L5-S1 and strain on the iliolumbar ligaments when protection from back muscles against lumbar flexion is absent. Lumbar backrest support almost eliminates lumbosacral and sacroiliac movement. RELEVANCE: Understanding why the iliolumbar ligaments are loaded in slouching contributes to the understanding of the biomechanics of low back pain in everyday situations with small or negligible compressive spinal load. The results recommend lumbar support: backrests with free shoulder space.

Protrusion of prosthetic meshes in repair of inguinal hernias.

BACKGROUND: Although techniques with prosthetic meshes have improved results of inguinal hernia repair, the problem of recurrence remains. In addition to patient- and surgeon-related causes, protrusion of prosthetic mesh through the hernia defect can be considered as a factor of recurrence. METHODS: To simulate inguinal hernia, porcine tissue with standardized defects (3, 4, and 5 cm) was used. Nine different meshes (9 cm diameter) were positioned on the defects. In a pressure chamber the depth of protrusion through the defect was assessed. Both sides of each mesh were measured. Protrusion at a pressure representing Valsalva pressure was used for statistical analysis. RESULTS: Protrusion, including the incidence of collapse, increased with larger defect sizes. Significant protrusion differences were found between different meshes and occasionally between the 2 sides of the same mesh. CONCLUSIONS: The differences between the effects of the various meshes emphasize the importance of material characteristics when developing new surgical techniques. The 3 meshes showing least protrusion are considered especially suitable when repairing large defects or when preferring a small mesh when repairing inguinal hernias with a preperitoneal sublay approach.

The iliolumbar ligament: its influence on stability of the sacroiliac joint.

STUDY DESIGN: In human specimens the influence of the iliolumbar ligament on sacroiliac joint stability was tested during incremental moments applied to the sacroiliac joints. OBJECTIVES: To assess whether the iliolumbar ligament is able to restrict sacroiliac joint mobility in embalmed cadavers. BACKGROUND: Firstly, the sacroiliac joint can play an important role in non-specific low back pain; hence, its mobility and stability are of special interest. Secondly, the iliolumbar ligament is considered to be an important source of chronic low back pain. Data on a functional relation between the iliolumbar ligament and sacroiliac joint mobility are lacking. METHODS: In 12 human specimens an incremental moment was applied to the sacroiliac joint to induce rotation in the sagittal plane. After the assessment of the relationship between rotation angle and moment in the intact situation, specific parts of the iliolumbar ligaments were transected. After each partial transection the measurements were repeated. RESULTS: Sacroiliac joint mobility in the sagittal plane was significantly increased after a total cut of both iliolumbar ligaments. This increase was in particular due to the transection of a specific part of the iliolumbar ligament, the ventral band. CONCLUSIONS: The main conclusions are: (a) the iliolumbar ligaments restrict sacroiliac joint sagittal mobility; (b) the ventral band of the iliolumbar ligament contributes most to this restriction. RELEVANCE: In embalmed human cadavers, the mobility of the sacroiliac joint increases after sequential cutting of specific parts of the iliolumbar ligaments. It can be expected that severance of this ligament during surgery will lead to increase of mobility and hence loss of stability of the sacroiliac joint. As a consequence adjacent structures will be affected. This may well be a cause of pain in patients with failed back surgery.