The effect of the amount of limb lengthening on skeletal muscle

Discussing Conflicting Explanatory Approaches in Flexibility Training Under Consideration of Physiology: A Narrative Review

The mechanisms underlying range of motion enhancements via flexibility training discussed in the literature show high heterogeneity in research methodology and study findings. In addition, scientific conclusions are mostly based on functional observations while studies considering the underlying physiology are less common. However, understanding the underlying mechanisms that contribute to an improved range of motion through stretching is crucial for conducting comparable studies with sound designs, optimising training routines and accurately interpreting resulting outcomes. While there seems to be no evidence to attribute acute range of motion increases as well as changes in muscle and tendon stiffness and pain perception specifically to stretching or foam rolling, the role of general warm-up effects is discussed in this paper. Additionally, the role of mechanical tension applied to greater muscle lengths for range of motion improvement will be discussed. Thus, it is suggested that physical training stressors can be seen as external stimuli that control gene expression via the targeted stimulation of transcription factors, leading to structural adaptations due to enhanced protein synthesis. Hence, the possible role of serial sarcomerogenesis in altering pain perception, reducing muscle stiffness and passive torque, or changes in the optimal joint angle for force development is considered as well as alternative interventions with a potential impact on anabolic pathways. As there are limited possibilities to directly measure serial sarcomere number, longitudinal muscle hypertrophy remains without direct evidence. The available literature does not demonstrate the necessity of only using specific flexibility training routines such as stretching to enhance acute or chronic range of motion.

Outcomes and Patient Satisfaction of Delayed Distal Biceps Repairs without Graft Augmentation: A Systematic Review

BACKGROUND

Distal biceps tendon tears are responsible for 3% to 10% of all biceps ruptures. Treated nonoperatively, these injuries result in poor endurance, loss of supination strength, and loss of flexion strength compared with those treated operatively with repair or reconstruction. When presenting in a chronic fashion, operative management can involve graft reconstruction or primary repair. When there is adequate tendon excursion and quality, primary repair is preferred. The purpose of this systematic review was to investigate the literature regarding outcomes of direct surgical repair of chronic distal biceps tendon ruptures.

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed to perform this systematic review and for the presentation of results. A search of the literature was performed on the electronic database Medline, Scopus, and the Cochrane Library. Included studies evaluated subjective and objective outcomes after delayed treatment (≥4 weeks postinjury) for chronic distal biceps tendon ruptures, without use of graft augmentation. Subjective and objective outcome metrics such as functional scores, range of motion, strength, pain level, and return to employment were collected.

RESULTS

Eight studies were reviewed. The studies included 124 patients with chronic distal biceps tendon tears, treated surgically after a mean delay to surgery of 121.8 days. Four studies included comparison of patients with acute and chronic tears, whereas the other 4 studies assessed chronic tears only. The findings of these 4 studies suggest that direct repair of chronic tears is correlated with a mildly higher rate of lateral antebrachial cutaneous nerve (LABCN) injury palsy (10/82 [12.1%] chronic vs. 3/38 [7.9%] acute, p = 0.753); however, this complication was overwhelmingly transient. There were only 3 reported reruptures (3.19%) across 5 studies reporting this complication. Overall, patients who had undergone direct repair of chronic distal biceps tears had good patient satisfaction, outcomes, and range of motion.

CONCLUSION

Direct repair of chronic distal biceps tendon tears without the use of graft reconstruction is associated with acceptable patient satisfaction, range of motion, and functional outcome scores, although transient LABCN palsy rates may be slightly higher. When sufficient residual tendon is present in the setting of chronic distal biceps rupture, direct repair is a viable treatment option. However, the existing literature regarding direct repair of chronic distal biceps repair is limited, and further prospective assessment directly comparing primary repair vs. reconstruction of chronic distal biceps ruptures is warranted.

LEVEL OF EVIDENCE

Level IV. See Instructions for Authors for a complete description of levels of evidence.

Gradual Correction of Pediatric Equinus Deformity

Pediatric equinus is broadly defined as generalized limited dorsiflexion at the ankle joint. It may result from either congenital or acquired causes and exhibit varying characteristics such as flexible, rigid, or spastic types. It has been extensively studied in literature and is known to be associated with the pathological condition of the bone, soft tissue, or combined deformity. In children, rigid plantarflexed cases can be debilitating and prevent them from ambulating without pain, if at all. As this volume in Clinics has chapters on comprehensive pediatric examination and neuromuscular disorders, this article will focus on (non-neurologic equinus) and its treatment via conservative and surgical methods with an emphasis on gradual correction.

Changes in Distribution of Lower Limb Alignment After Total Hip Arthroplasty for Crowe IV Developmental Dysplasia of the Hip

Purpose

The purpose of this study was to evaluate the distribution of lower limb alignment in Crowe IV developmental dysplasia of the hip (DDH) before and after total hip arthroplasty (THA).

Patients and Methods

We retrospectively included 64 Crowe IV DDH patients (87 hips) who underwent THA between February 2010 and May 2019. Radiographic parameters were measured on full limb length standing anteroposterior radiographs, including hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), anatomical lateral distal femoral angle (aLDFA), and anatomical tibiofemoral angle (aTFA).

Results

HKA improved from 176.54°±3.52° preoperatively to 179.45°±4.31° at the last followup (P<0.001). According to the preoperative HKA, 40 hips were defined as knee valgus alignment. The majority of them were characteristic of a valgus mLDFA and a valgus or neutral mMPTA (35%, 47.5%). After THA, there were still 22 hips defined as knee valgus alignment. More than 50% of them were characteristic of a valgus mLDFA and a neutral mMPTA. Five hips (22.7%) revealed valgus alignment in both mLDFA and mMPTA. Twenty-one hips (24.1%) remained knee valgus alignment before and after surgery. One hip, defined as neutral alignment, preoperatively turned into valgus alignment after surgery.

Conclusion

Both preoperative and postoperative sources of valgus alignment were mainly from the femoral side among Crowe IV DDH patients. THA mainly played a positive role in the reconstruction of lower limb alignment in these patients.

Changes in Muscle Stress and Sarcomere Adaptation in Mice Following Ischemic Stroke

While abnormal muscle tone has been observed in people with stroke, how these changes in muscle tension affect sarcomere morphology remains unclear. The purpose of this study was to examine time-course changes in passive muscle fiber tension and sarcomeric adaptation to these changes post-ischemic stroke in a mouse model by using a novel in-vivo force microscope. Twenty-one mice were evenly divided into three groups based on the time point of testing: 3 days (D3), 10 days (D10), and 20 days (D20) following right middle cerebral artery ligation. At each testing time, the muscle length, width, and estimated volume of the isolated soleus muscle were recorded, subsequently followed by in-vivo muscle tension and sarcomere length measurement. The mass of the soleus muscle was measured at the end of testing to calculate muscle density. Two-way ANOVA with repeated measures was used to examine the differences in each of the dependent variable among the three time-point groups and between the two legs. The passive muscle stress of the impaired limbs in the D3 group (27.65 ± 8.37 kPa) was significantly lower than the less involved limbs (42.03 ± 18.61 kPa; p = 0.05) and the impaired limbs of the D10 (48.92 ± 14.73; p = 0.03) and D20 (53.28 ± 20.54 kPa; p = 0.01) groups. The soleus muscle density of the impaired limbs in the D3 group (0.69 ± 0.12 g/cm3) was significantly lower than the less involved limbs (0.80 ± 0.09 g/cm3; p = 0.04) and the impaired limbs of the D10 (0.87 ± 0.12 g/cm3; p = 0.02) and D20 (1.00 ± 0.14 g/cm3; p < 0.01) groups. The D3 group had a shorter sarcomere length (2.55 ± 0.26 μm) than the D10 (2.83 ± 0.20 μm; p = 0.03) and D20 group (2.81 ± 0.15 μm; p = 0.04). These results suggest that, while ischemic stroke may cause considerable changes in muscle tension and stress, sarcomere additions under increased mechanical loadings may be absent or disrupted post-stroke, which may contribute to muscle spasticity and/or joint contracture commonly observed in patients following stroke.

Mechanical Influence of Surrounding Soft Tissue on Bone Regeneration Processes: A Bone Lengthening Study

Bone lengthening is a bone regeneration technique with multiple clinical applications. One of the most common complications of this treatment is the lack of adaptation of the surrounding soft tissue to their extension. A better understanding of the mechanobiology of the tissues involved in distraction osteogenesis would allow better control of the clinical cases. Bone lengthening treatments were performed in vivo in the metatarsus of Merino sheep, measuring the distraction forces by means of an instrumented fixator. The tissue relaxation after distraction was analyzed in this study. A viscoelastic model was also applied to distraction data to assess the mechanical behavior of the tissues during the distraction phase. Tissue relaxation is similar to other bone regeneration processes which do not imply surrounding soft tissue extension, e.g. bone transport. The effects of this tissue on distraction forces are limited to the first minutes of distraction and elongations above 4% of the original length with the protocol applied. Moreover, the surrounding soft tissue initially loses some of its viscoelasticity and subsequently suffers strain hardening from day 5 of distraction until the end of the distraction phase, day 15. Finally, anatomical changes were also evidenced in the elongated limb of our specimens.

Identifying the Structural Adaptations that Drive the Mechanical Load-Induced Growth of Skeletal Muscle: A Scoping Review

The maintenance of skeletal muscle mass plays a critical role in health and quality of life. One of the most potent regulators of skeletal muscle mass is mechanical loading, and numerous studies have led to a reasonably clear understanding of the macroscopic and microscopic changes that occur when the mechanical environment is altered. For instance, an increase in mechanical loading induces a growth response that is mediated, at least in part, by an increase in the cross-sectional area of the myofibers (i.e., myofiber hypertrophy). However, very little is known about the ultrastructural adaptations that drive this response. Even the most basic questions, such as whether mechanical load-induced myofiber hypertrophy is mediated by an increase in the size of the pre-existing myofibrils and/or an increase in the number myofibrils, have not been resolved. In this review, we thoroughly summarize what is currently known about the macroscopic, microscopic and ultrastructural changes that drive mechanical load-induced growth and highlight the critical gaps in knowledge that need to be filled.

Distal biceps tendon ruptures - the relation of radiological retraction and chronicity to the ability of tendon reattachment and long-term functional outcomes

Aims

To assess whether the degree of radiological retraction and chronicity of distal biceps tendon ruptures are related to the ability to reattach the tendon and long-term functional outcomes.

Methods

Analysis of consecutive patients undergoing surgery for distal biceps tendon ruptures by a single surgeon. Measurements regarding the site and degree of tendon retraction in relation to anatomical landmarks following rupture were correlated with intraoperative findings. Postoperative functional outcomes were assessed in cases with >12 months follow-up.

Results

24 cases of distal biceps tendon ruptures treated surgically were identified. Mean tendon retraction was 6.0 cm (range 1.2-9.5) from the radial tuberosity. 22 cases were reattached successfully. 2 required ligament augmentation/bridging using a synthetic ligament. In 2 cases the tendon could not be reattached due to poor quality of the tendon stump. Ability to reattach the tendon was unrelated to degree of radiological retraction or chronicity of rupture. Degree of retraction was not related to rupture chronicity. All reattachments healed with no re-rupture at follow-up with no substantial motion loss. In 17 cases >12months follow-up the DASH and OES were not related to retraction or chronicity of rupture.

Conclusions

Radiological retraction and chronicity are not related to the ability to reattach distal biceps tendon ruptures or their clinical outcomes, hence should not discourage surgical exploration and attempted reattachment. Substantial tendon retractions can occur acutely and reattachment in considerable flexion did not produce any significant motion loss. Some cases will need augmentation or gap bridging and augmentation devices need to be available at surgery.

Level of evidence

Level IV Retrospective Study Defined.

The Association of Tibia Femur Ratio and Degenerative Disease of the Spine, Hips, and Knees

BACKGROUND

When individuals with asymmetric lower extremities present for evaluation of limb-length inequality, correction can occur at the tibia, femur, or in both bones; however, there are limited data available to justify either technique. The aim of this study is to examine the normal ratio of tibia length/femur length (T/F), and to explore the relationship between T/F ratio and osteoarthritis of the spine, hips, and knees.

METHODS

Bone lengths of 1152 cadaveric femora and tibiae from the Hamann-Todd osteological collection were measured. Degenerative joint disease was graded in the hip, knee, and spine. Correlations between the ratio of T/F and osteoarthritis were evaluated with multiple regression analysis.

RESULTS

The average ratio of T/F was 0.80±0.03. There was a strong correlation between age and arthritis at all sites, with standardized β ranging from 0.44 to 0.57 (P<0.0005 for all). There was a significant correlation between increasing T/F and hip arthritis (standardized β=0.08, P=0.006), and knee arthritis (standardized β=0.08, P=0.008).

DISCUSSION

Increasing tibia length relative to femur length was found to be a significant predictor of ipsilateral hip and knee arthritis. Therefore, we recommend that when performing limb lengthening, surgical planning should lean toward recreating the normal ratio of 0.80. In circumstances where one bone is to be overlengthened relative to the other, bias should be toward overlengthening the femur. This same principle can be applied to limb-reduction surgery, where in certain circumstances, one may choose to preferentially shorten the tibia.

CLINICAL RELEVANCE

This is the first study to report long-term consequences of lower extremity segment disproportion.

Is Botulinum Toxin Type A a Valuable Adjunct During Femoral Lengthening? A Randomized Trial

BACKGROUND

Reduced joint ROM and distraction-induced pain are common complaints of patients who have undergone gradual femoral lengthening. Attempts to reduce the effects of lengthening on joint motion have included the use of botulinum toxin to reduce the muscle forces that restrict motion. The benefits of this approach during femoral lengthening, however, have not been conclusively established.

QUESTIONS/PURPOSES

We wished to evaluate the effects of botulinum toxin type A (BtX-A) injection in the anterior thigh muscles during femoral distraction osteogenesis on adjacent joint ROM and distraction-induced pain. We asked: (1) Does injection of BtX-A in the quadriceps muscles lead to improved knee and hip motion during femoral lengthening? (2) Does injection of BtX-A reduce pain during femoral lengthening?

METHODS

A single-center, double-blind, randomized placebo-controlled trial was conducted. Forty-four patients (88 femurs) undergoing bilateral femoral lengthening for familial short stature were included in the study. BtX-A (200 IU) was injected intraoperatively in the quadriceps muscles of one thigh. An equal volume of sterile normal saline was injected in the other thigh as a control. Selection of the limb receiving the toxin was randomized. Clinical evaluation included a VAS score for pain measurement, ROM evaluation of the hips and knees, and measurement of thigh circumference. Side-to-side differences were analyzed throughout the entire consolidation phase. No patients were lost to followup, leaving 44 patients (88 femurs). The mean followup was 26 months (range, 14-40 months). The distraction rate and final length of gain were similar between treated and control limbs. A priori power analysis suggested that 44 legs were required in each group to achieve statistical significance of 0.05 with 90% power to detect a 50% difference in treatment effect between treatment and control groups.

RESULTS

There were no differences in hip ROM, knee ROM, or maximal thigh circumference between the two lower extremities at any time during the study period. VAS scores were no different between the patients who received BtX-A and those who received saline.

CONCLUSIONS

Local injection of 200 IU BtX-A in the quadriceps muscles does not appear to reduce distraction-induced pain nor enhance ROM in the hip or knee during femoral lengthening. Additional studies are needed to evaluate the effect of larger doses or different injection methods. Based on our findings, we do not recommend routine use of botulinum injections during limb lengthening and believe any further use of this drug should only be in the context of a controlled trial.

LEVEL OF EVIDENCE

Level II, therapeutic study.

High resolution muscle measurements provide insights into equinus contractures in patients with cerebral palsy

Muscle contractures that occur after upper motor neuron lesion are often surgically released or lengthened. However, surgical manipulation of muscle length changes a muscle's sarcomere length (Ls ), which can affect force production. To predict effects of surgery, both macro- (fascicle length (Lf )) and micro- (Ls ) level structural measurements are needed. Therefore, the purpose of this study was to quantify both Ls and Lf in patients with cerebral palsy (CP) as well as typically developing (TD) children. Soleus ultrasound images were obtained from children with CP and TD children. Lf was determined and, with the joint in the same position, CP biopsies were obtained and formalin fixed, and Ls was measured by laser diffraction. Since soleus Ls values were not measurable in TD children, TD Ls values were obtained using three independent methods. While average Lf did not differ between groups (CP=3.6±1.2 cm, TD=3.5±0.9 cm; p>0.6), Ls was dramatically longer in children with CP (4.07±0.45 µm vs. TD=2.17±0.24 µm; p<0.0001). While Lf values were similar between children with CP and TD children, this was due to highly stretched sarcomeres within the soleus muscle. Surgical manipulation of muscle-tendon unit length will thus alter muscle sarcomere length and change force generating capacity of the muscle.

Botulinum toxin a does not decrease calf pain or improve ROM during limb lengthening: a randomized trial

BACKGROUND

During lower limb lengthening, distraction-induced muscle pain and surrounding joint contractures are frustrating complications for which few effective treatments are available.

QUESTIONS/PURPOSES

We evaluated Botulinum Toxin Type A (BtX-A) injection in the calf muscles during human tibial distraction osteogenesis. We hypothesized that it may decrease calf pain and increase ROM of the surrounding joints by reducing muscle stiffness.

METHODS

Between April 2010 and January 2011, we evaluated 36 patients undergoing bilateral tibia lengthening who met prespecified inclusion criteria. All patients underwent stature lengthening with lengthening over a nail or lengthening and then nailing. BtX-A (200 IU) was injected at the calf muscle only in one leg for each patient and the same amount of sterile normal saline was injected into the other leg as a control. Selection of the leg receiving the toxin was randomized. Clinical evaluation included a VAS score for calf pain and measurement of ROM of the knees and ankles and calf circumference, with evaluations performed in a double-blinded manner. Side-to-side differences were analyzed until the end of consolidation phase. Minimum followup was 24 months (mean, 30 months; range, 24-39 months). The distraction rate and the final length gain were similar in the treated and control limbs. A priori power analysis suggested that 34 legs were required to achieve statistical significance of 0.05 with 80% of power to detect a 50% difference in treatment effect between treatment and control groups.

RESULTS

There were no differences in calf pain, knee and ankle ROM, and maximal calf circumferences between the two legs at each time point.

CONCLUSIONS

Local injection of 200 IU BtX-A at the human calf muscle does not appear to reduce calf pain or help enhance ROM of the knee and ankle during tibial lengthening. However, the small sample size provided sufficient power to detect only relatively large clinical effects; future, larger trials will be needed to determine whether smaller differences are present.

LEVEL OF EVIDENCE

Level II, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Bone marrow aspirate concentrate and platelet-rich plasma enhanced bone healing in distraction osteogenesis of the tibia

BACKGROUND

During lower limb lengthening, poor bone regeneration is a devastating complication. Several local or systemic applications have been used to promote osteogenesis, and biologic stimulations are gaining attention, but their utility has not been proven in this setting.

QUESTIONS/PURPOSES

In patients undergoing bilateral tibial lengthening, we compared those receiving an osteotomy site injection of autologous bone marrow aspirate concentrate (BMAC) plus platelet-rich plasma (PRP) with those not receiving such an injection in terms of external fixator index (time in external fixation divided by amount of lengthening), full weightbearing index (time until a patient was permitted to do full weightbearing divided by amount of lengthening), four cortical healing indexes (time until each cortical union divided by amount of lengthening), and callus shape and type.

METHODS

Twenty-two patients (44 tibias) undergoing bilateral tibial lengthening enrolled in this randomized trial. Two patients were excluded, one due to insufficient radiographic evaluation and one who was lost to followup, leaving 20 patients (40 segments) for inclusion. Ten patients (20 segments) received BMAC combined with PRP injection (treatment group) and 10 patients (20 segments) received no injection (control group). All patients underwent stature lengthening for familial short stature with the lengthening over nail technique. Autologous BMAC combined with PRP was injected at the tibial osteotomy site at the end of the index surgery. Mean distraction rates were similar between groups (0.75 mm/day in the treatment group versus 0.72 mm/day in the control group; p = 0.24). Full weightbearing was permitted when we observed radiographic evidence of healing at two cortices; this assessment was made by the surgeon who was blinded to the treatment each patient received. Minimum followup was 24 months (mean, 28 months; range, 24-34 months).

RESULTS

There was no difference in mean external fixator index between groups. However, mean cortical healing indexes (anterior/posterior/medial/lateral) were 1.14/0.81/0.96/0.88 months/cm in the treatment group and 1.47/1.26/1.42/1.22 months/cm in the control group (all p < 0.001), showing faster healing in the treatment group at each cortex. Full weightbearing was permitted earlier in the treatment group than in the control group (index: 0.99 months/cm and 1.38 months/cm, respectively, p < 0.001). Callus shape and type were not different between groups.

CONCLUSIONS

Autologous BMAC combined with PRP injection at the osteotomy site helped improve bone healing in distraction osteogenesis of the tibia, although the effect size was small.

LEVEL OF EVIDENCE

Level I, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Quantitative and temporal differential recovery of articular and muscular limitations of knee joint contractures; results in a rat model

Joint contractures alter the mechanical properties of articular and muscular structures. Reversibility of a contracture depends on the restoration of the elasticity of both structures. We determined the differential contribution of articular and muscular structures to knee flexion contractures during spontaneous recovery. Rats (250, divided into 24 groups) had one knee joint surgically fixed in flexion for six different durations, from 1 to 32 wk, creating joint contractures of various severities. After the fixation was removed, the animals were left to spontaneously recover for 1 to 48 wk. After the recovery periods, animals were killed and the knee extension was measured before and after division of the transarticular posterior muscles using a motorized arthrometer. No articular limitation had developed in contracture of recent onset (≤2 wk of fixation, P > 0.05); muscular limitations were responsible for the majority of the contracture (34 ± 8° and 38 ± 6°, respectively; both P < 0.05). Recovery for 1 and 8 wk reversed the muscular limitation of contractures of recent onset (1 and 2 wk of fixation, respectively). Long-lasting contractures (≥4 wk of fixation) presented articular limitations, irreversible in all 12 durations of recovery compared with controls (all 12 P < 0.05). Knee flexion contractures of recent onset were primarily due to muscular structures, and they were reversible during spontaneous recovery. Long-lasting contractures were primarily due to articular structures and were irreversible. Comprehensive temporal and quantitative data on the differential reversibility of mechanically significant alterations in articular and muscular structures represent novel evidence on which to base clinical practice.

Use it or lose it: multiscale skeletal muscle adaptation to mechanical stimuli

Skeletal muscle undergoes continuous turnover to adapt to changes in its mechanical environment. Overload increases muscle mass, whereas underload decreases muscle mass. These changes are correlated with, and enabled by, structural alterations across the molecular, subcellular, cellular, tissue, and organ scales. Despite extensive research on muscle adaptation at the individual scales, the interaction of the underlying mechanisms across the scales remains poorly understood. Here, we present a thorough review and a broad classification of multiscale muscle adaptation in response to a variety of mechanical stimuli. From this classification, we suggest that a mathematical model for skeletal muscle adaptation should include the four major stimuli, overstretch, understretch, overload, and underload, and the five key players in skeletal muscle adaptation, myosin heavy chain isoform, serial sarcomere number, parallel sarcomere number, pennation angle, and extracellular matrix composition. Including this information in multiscale computational models of muscle will shape our understanding of the interacting mechanisms of skeletal muscle adaptation across the scales. Ultimately, this will allow us to rationalize the design of exercise and rehabilitation programs, and improve the long-term success of interventional treatment in musculoskeletal disease.

Primary repair of retracted distal biceps tendon ruptures in extreme flexion

BACKGROUND

Distal biceps tendon ruptures may have tendinous retraction, making primary repair difficult and calling into question the need for graft reconstruction. The decision for when to primarily fix or augment high-flexion repairs has not been addressed. We hypothesized high-flexion repairs would have good outcomes without graft augmentation. The purpose of this study was to examine allograft use and outcomes of distal biceps tendon ruptures requiring repair in greater than 60° of flexion.

METHODS

This was a retrospective case-control study 188 distal biceps tendon repairs; of these, 19 chronic and 4 acute cases were identified with repairs of >60° of flexion using a 2-incision technique. Graft need, complications, and Mayo Elbow Performance Score to assess function, were examined with a record review. Patients were surveyed regarding return to work and subjective satisfaction. A control group matched for surgeon, chronicity, and age, but without a high-flexion repair, was compared with cases by using the Student paired t test.

RESULTS

Graft augmentation was used in 1 patient with poor tendon quality. The Mayo Elbow Performance Score was 100 for all 23 patients, with extension/flexion range of motion from 3° to 138°. All were subjectively "very satisfied/satisfied," with full work return, yet 3 reported mild fatigability. There were 4 complications: 3 transient lateral antebrachial cutaneous neurapraxias and 1 rerupture at the myotendinous junction after retrauma. Differences between cases and controls were not statistically significant.

CONCLUSION

Contracted distal biceps tendons may be reliably reattached to their anatomic insertion with up to 90° of elbow flexion. This lessens the need for reconstruction in such circumstances.

Structural adaptations of rat lateral gastrocnemius muscle-tendon complex to a chronic stretching program and their quantification based on ultrasound biomicroscopy and optical microscopic images

BACKGROUND

A chronic regimen of flexibility training can increase range of motion, with the increase mechanisms believed to be a change in the muscle material properties or in the neural components associated with this type of training.

METHODS

This study followed chronic structural adaptations of lateral gastrocnemius muscle of rats submitted to stretching training (3 times a week during 8weeks), based on muscle architecture measurements including pennation angle, muscle thickness and tendon length obtained from ultrasound biomicroscopic images, in vivo. Fiber length and sarcomere number per 100μm were determined in 3 fibers of each muscle (ex vivo and in vitro, respectively), using conventional optical microscopy.

FINDINGS

Stretching training resulted in a significant pennation angle reduction of the stretched leg after 12 sessions (25%, P=0.002 to 0.024). Muscle thickness and tendon length presented no significant changes. Fiber length presented a significant increase for the stretched leg (8.5%, P=0.00006), with the simultaneous increase in sarcomere length (5%, P=0.041) since the stretched muscles presented less sarcomeres per 100μm.

INTERPRETATION

A stretching protocol with characteristics similar to those applied in humans was sufficient to modify muscle architecture of rats with absence of a sarcomerogenesis process. The results indicate that structural adaptations take place in skeletal muscle tissue submitted to moderate-intensity stretching training.

Foot and ankle function after tibial overlengthening

Lengthening the tibia more than 25% of its original length can be indicated for proximal femoral deficiency, poliomyelitis, or femoral infected nonunion. Such lengthening of the tibia can adversely affect the ankle or foot shape and function. The present study aimed to assess the effect of tibial lengthening of more than 25% of its original length on the foot and ankle shape and function compared with the preoperative condition. This was a retrospective study of 13 children with severe proximal focal femoral deficiency, Aitken classification type D, who had undergone limb lengthening from June 2000 to June 2008 using Ilizarov external fixators. The techniques used in tibial lengthening included lengthening without intramedullary rodding and lengthening over a nail. The foot assessment was done preoperatively, at fixator removal, and then annually for 3 years, documenting the range of motion and deformity of the ankle and subtalar joints and big toe and the navicular height, calcaneal pitch angle, and talo-first metatarsal angle. At fixator removal, all cases showed equinocavovarus deformity, with decreased ankle, subtalar, and big toe motion. The mean American Orthopedic Foot and Ankle Society score was significantly reduced. During follow-up, the range of motion, foot deformity, and American Orthopedic Foot and Ankle Society score improved, reaching nearly to the preoperative condition by 2 years of follow-up. The results of our study have shown that tibial overlengthening has an adverse effect on foot and ankle function. This effect was reversible in the patients included in the present study. Lengthening of more than 25% can be safely done after careful discussion with the patients and their families about the probable effects of lengthening on foot and ankle function.

Muscle excursion does not correlate with increased serial sarcomere number after muscle adaptation to stretched tendon transfer

Chronic skeletal muscle stretch typically increases serial muscle fiber sarcomere number. Since serial sarcomere number correlates with functional excursion in normal muscle, observed changes in sarcomere number are often extrapolated to their new assumed function. However, this has not been well demonstrated experimentally. Thus, we measured the functional properties of muscles stretched due to tendon transfer surgery. Muscle active and passive length-tension curves were measured 1 week and 4 weeks after surgery, and then each muscle was further examined to determine structural adaptation as well as single fiber and fiber bundle passive mechanical properties. We found a disconnect between the functional and structural muscle properties. Specifically, muscle excursion was significantly lower in the transferred muscle compared to controls, even though serial sarcomere number had increased. Furthermore, maximum tetanic tension was significantly reduced, though the two groups had similar physiological cross sectional areas. Passive tension increased in the transferred muscle, which was deemed to be due to proliferation of extracellular matrix. These data are the first to report that muscle morphological adaptation after chronic stretch does not accurately predict the muscle's functional properties. These data have significant implications for examining muscle physiological properties under surgical interventions.

A rabbit model for studying degeneration and regeneration properties of young striated muscle at different distraction rates

The present study evaluated the histological changes in the muscle tissue after limb lengthening in skeletally immature rabbits and assessed the effect of different lengthening rates on the regeneration and degeneration properties of striated muscle. Thirteen different lengthening protocols were applied on a total of 16 male domestic white rabbits divided into four groups. The histopathological changes were analysed by a semiquantitative method according to the scoring system of Lee et al. (1993). After evaluation of the five main degenerative parameters (muscle atrophy, internalisation of muscle nuclei, degeneration of the muscle fibre, perimysial and endomysial fibrosis, haematomas), it is evident that rabbits subjected to limb lengthening at a rate of 3.2 mm/day showed more degenerative changes than those limb-lengthened at 0.8 or 1.6 mm/day. Our study showed that the regenerative mechanisms were not endless. If the daily lengthening rate reached the 3.2 mm/day limit, the regenerating ability of the muscle decreased, and signs of degeneration increased significantly.

Recovery of muscle strength and power after limb-lengthening surgery

OBJECTIVE

To report muscle strength, power, and function after limb-lengthening surgery performed by using the Ilizarov technique.

DESIGN

Prospective, longitudinal observational study of a cohort of consecutive patients who underwent limb-lengthening distraction followed up for 2 years after surgery.

SETTING

National Health Service hospital specializing in orthopedic surgery.

PARTICIPANTS

Patients (N=16) who had undergone limb-lengthening surgery performed by using the Ilizarov method (11 men, 5 women; mean age=27 y; range, 13-56 y).

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Muscle strength and power were assessed by using 2 validated measures: isokinetic concentric strength of the quadriceps and hamstrings measured by using a dynamometer and leg extensor power. Measures were recorded preoperatively and at 6, 12, and 24 months after the completion of lengthening. Function was measured by 2 timed tests of functional performance: stair climbing and sit-to-stand.

RESULTS

Overall results were good with high reports of function and satisfactory clinical examination. Both concentric muscle strength and leg power showed a clear pattern of decreased muscle strength at 6 months after frame removal, improving throughout the study period until it was within 3% of the preoperative value at 2 years. By 2 years, self-reported function and ability to complete timed functional tests had returned to or improved on the preoperative values. Muscle strength remained slightly below the preoperative value; this was more pronounced in the quadriceps than the hamstrings. There was no association between muscle strength and the amount of lengthening that had been undertaken.

CONCLUSIONS

This study suggests that there is a small residual decrease in muscle strength and power after limb-lengthening surgery but that these do not adversely impact on a patients' ability to perform everyday functional activities.

Sarcomere length of torn rotator cuff muscle

BACKGROUND

Sarcomere length is one of the factors related to the contractile ability of muscle. There is no report about sarcomere length of torn rotator cuff muscles. The purpose of this study was to clarify sarcomere length of torn rotator cuff muscles.

MATERIALS AND METHODS

Twenty-eight embalmed cadaver shoulders (14 shoulders with intact rotator cuff and 14 shoulders with full-thickness rotator cuff tears: an isolated tear of the supraspinatus in 3, a combined tear of the supraspinatus and infraspinatus in 4, and a combined tear of the supraspinatus, infraspinatus and subscapularis in 7) were used in this study. Muscle fiber length was measured using a digital caliper. Sarcomere length was measured by laser diffraction method.

RESULTS

Muscle fiber lengths of the supraspinatus and infraspinatus (33.0 +/- 6.5 mm and 61.5 +/- 14.0 mm, respectively) in the cuff tear group were significantly shorter than those in the intact cuff group (56.9 +/- 10.1 mm and 74.2 +/- 10.0 mm: P < .001 and P = .010). The sarcomere lengths of these muscles were 3.00 +/- 0.44 microm and 3.12 +/- 0.45 microm in the intact cuff group and 2.90 +/- 0.34 microm and 3.01 +/- 0.34 microm in the cuff tear group. The sarcomere lengths showed no significant difference (P = 0.46 and P = .37).

CONCLUSION

The sarcomere lengths of the supraspinatus and infraspinatus with torn tendons were not significantly different from those with intact tendons, although the muscle fiber lengths were significantly shorter with torn tendons.

Structural changes in the lengthened rabbit muscle

This study evaluated the histological changes in muscle tissue after limb lengthening in skeletally mature and immature rabbits and assessed the most vulnerable level of striated muscle. Twenty-three male domestic white rabbits, divided into six groups, were operated on and different lengthening protocols were used in the mature and immature rabbits. The histopathological changes were analysed by a semi-quantitative method according to the scoring system of Lee et al. (Acta Orthop Scand 64(6):688-692, 1993). After the evaluation of the five main degenerative parameters (muscle atrophy, muscle nuclei internalisation, degeneration of the muscle fibre, perimysial and endomysial fibrosis, haematomas), it is evident that the adults lengthened at a rate of 1.6 mm/day showed more degenerative changes than those lengthened at 0.8 mm/day. The adult 1.6 mm/day lengthened group presented significantly higher damage in the muscle and lower regenerative signs compared with the young 1.6 mm/day lengthened group, according to the summarised degenerative scores.

Safety and efficacy of botox injection in alleviating post-operative pain and improving quality of life in lower extremity limb lengthening and deformity correction

BACKGROUND

Distraction osteogenesis is the standard treatment for the management of lower limb length discrepancy of more than 3 cm and bone loss secondary to congenital anomalies, trauma or infection. This technique consists of an osteotomy of the bone to be lengthened, application of an external fixator, followed by gradual and controlled distraction of the bone ends. Although limb lengthening using the Ilizarov distraction osteogenesis principle yields excellent results in most cases, the technique has numerous problems and is not well tolerated by many children. The objective of the current study is to determine if Botulinum Toxin A (BTX-A), which is known to possess both analgesic and paralytic actions, can be used to alleviate post-operative pain and improve the functional outcome of children undergoing distraction osteogenesis.

METHODS/DESIGN

The study design consists of a multi centre, randomized, double-blinded, placebo-controlled trial. Patients between ages 5-21 years requiring limb lengthening or deformity correction using distraction will be recruited from 6 different sites (Shriners Hospital for Children in Montreal, Honolulu, Philadelphia and Portland as well as DuPont Hospital for Children in Wilmington, Delaware and Hospital for Sick Children in Toronto, Ont). Approximately 150 subjects will be recruited over 2 years and will be randomized to either receive 10 units per Kg of BTX-A or normal saline (control group) intraoperatively following the surgery. Functional outcome effects will be assessed using pain scores, medication dosages, range of motion, flexibility, strength, mobility function and quality of life of the patient. IRB approval was obtained from all sites and adverse reactions will be monitored vigorously and reported to IRB, FDA and Health Canada.

DISCUSSION

BTX-A injection has been widely used world wide with no major side effects reported. However, to the best of our knowledge, this is the first time BTX-A is being used under the context of limb lengthening and deformity correction.

TRIAL REGISTRATION

NCT00412035.

Changes in pennate muscle architecture after gradual tibial lengthening in goats

The purpose of this investigation was to examine the changes in unipennate muscle architecture after distraction osteogenesis. Nine adult goats underwent 20% tibial lengthening in one of the hind limbs. Immediately after distraction, lengthened and contralateral (untreated) tibialis caudalis (TC) muscles were harvested. Lengths of the muscle belly, muscle fiber (FL), sarcomere (SL), tendon (TL), and superficial aponeurosis, as well as muscle mass, pennation angle (PA), and physiological cross-sectional area (PCSA), were compared between the treated and contralateral sides. Lengthened TC muscle demonstrated 20.8% increase in belly length, 4.39% increase in TL, and 36.7% increase in FL, while PA decreased by 37.2% (P = 008). Muscle length increase was mainly due to lengthening of muscle belly, which resulted both from FL increase and 15.3% length increase in the aponeurosis component of muscle belly, without significant effect of the PA decrease. The FL increase was due to SL increase, not to sarcomere neogenesis, while mass and PCSA did not change. We concluded that although muscle architecture can be adversely affected by distraction because of deficient sarcomere neogenesis, PCSA can remain unchanged, giving false impression of preserved function. Change in PA plays only minimal role in muscle adaptation to distraction.

Effects of botulinum toxin A on functional outcome during distraction osteogenesis

Distraction osteogenesis is useful for correcting limb length inequality, deformities, or short stature. Despite success with bone formation, soft tissue maladaptations including muscle and joint contracture may lead to undesirable results. Botulinum toxin A has been useful in treating spasticity in cerebral palsy, and has been used clinically in select cases to allay contracture in distraction osteogenesis. This study examines the toxin's efficacy in preventing distraction-induced loss of muscle strength and range of motion. The left tibias of 15 New Zealand White rabbits were distracted 1.5 mm/day until approximately a 20% gain was achieved. Each treatment group was divided into animals injected with saline or botulinum toxin in either the gastrocnemius or tibialis anterior muscles. A control group of two additional animals underwent no surgical procedure. Strength and range of motion were assessed prior to, and following, the experiment. At the study's end, animals were euthanized and muscles were harvested, when lengths and weights were recorded. All muscles injected with botulinum toxin showed decreased wet weight and persistent weakness upon completion of the study. Range of motion decreased in all distracted animals. When the gastrocnemius was injected, its strength was reduced but the tibialis anterior strength was preserved, and the limb achieved 22% greater dorsiflexion than saline controls (p = 0.016). When the tibialis anterior received the toxin, plantarflexion was increased by 23% (p = 0.049). Botulinum toxin injection prior to limb distraction increases the "post-lengthened" excursion of the injected muscle and this increased length may have a protective effect on its antagonist. In toxin-injected gastrocnemius muscles, the level of equinus contracture is reduced due to length gains in the Achilles tendon while the anterior tibialis maintains its ability to generate torque. Injection of botulinum toxin in the gastrocnemius may minimize equinus contracture and protect the anterior tibialis from damage during human tibial lengthening. Longer follow-up studies are needed to ensure that toxin-induced muscle weakness resolves with time.

Neuromuscular recovery after distraction osteogenesis at different frequencies in a rabbit model

The muscle and nerve responses to stresses applied during distraction osteogenesis have not been clearly defined. This study hypothesized that distraction resulting in 30% lengthening decreases muscle force generation of the lengthened muscle and increasing the frequency of distraction attenuates the decrease of force generation accompanying lengthening. This study investigated the effects of different distraction frequencies on neuromuscular recovery in a rabbit model. Animals were assigned into group 1 (low-frequency distraction) and group 2 (high-frequency distraction). Distraction was continued until a 30% increase in the original tibial length was achieved. After consolidation of the osteotomy, knee and ankle range of motion, muscle force generation, and neuromuscular junction parameters were evaluated. Lengthening of 30% resulted in significantly decreased range of motion compared with the control leg (P < 0.05). Lengthening of 30% also substantially decreased force generation of the peroneus longus muscle. However, force generation of the peroneus longus muscle in the high-frequency group was 70.5% +/- 6.5% of the control side, significantly higher than that in the low-frequency distraction group (49.7% +/- 4.8% of the control side, P < 0.05). There was no statistical difference between the 2 groups in neuromuscular junction morphology, although an abnormal shape of the postsynaptic neuromuscular junction was observed after distraction. The use of a high-frequency distraction technique during limb lengthening may result in a reduction in impairment of knee and ankle range of motion and improved muscle function compared with that observed with the use of low-frequency distraction. Repeated microtrauma to the soft tissues associated with high-frequency distraction may facilitate the regenerative capacity of the soft tissues and result in an improved outcome of muscle and nerve function.

Response of rabbit skeletal muscle to tibial lengthening

BACKGROUND

Experimental and clinical studies have provided knowledge regarding osteogenesis during limb lengthening. However, response of skeletal muscle to limb lengthening is not fully understood, especially as concerns histogenesis. We studied the morphological response of rabbit skeletal muscle to limb lengthening. In this study, we investigated proliferation of satellite cells, responsible for generation of new myonuclei, during limb lengthening.

METHODS

Tibialis anterior muscles of young and adult rabbits were subjected to lengthening at a rate of 0.5 mm twice per day for 20 days. After lengthening, muscle wet weight was measured to assess skeletal muscle growth, then proliferating cell nuclear antigen was measured. Immunostaining was performed to analyze proliferating cells in the proximal, middle, and distal portions of the muscle belly and the musculotendinous junction.

RESULTS

Muscle wet weight increased significantly after lengthening both in adult (0.4 g) and young (0.1 g) rabbits. Satellite cells showed proliferation in response to lengthening. In adult rabbits, satellite cell proliferation increased along the entire lengthened muscle to a similar degree (from 7.1% in the middle portion to 8.6% in the musculotendinous junction). In young rabbits, proliferation was greater in the musculotendinous junction (4.8%) than that in other muscle portions (2.3% in the middle and distal portions, and 2.4% in the proximal portion). In adult rabbits, the rate of increase in satellite cell proliferation was 1780% in the middle portion to 2860% in the musculotendinous junction, whereas the rate was between 210% in the middle portion and 290% in the distal portion in young rabbit. The rate of increase in cell proliferation by lengthening was higher in adult muscle than that in young muscles as well as satellite cell proliferation.

CONCLUSION

These findings indicate that limb lengthening promotes muscle growth in both young and adult rabbits.

The magnitude of muscle strain does not influence serial sarcomere number adaptations following eccentric exercise

It is generally accepted that eccentric exercise, when performed by a muscle that is unaccustomed to that type of contraction, results in a delayed onset of muscle soreness (DOMS). A prolonged exposure to eccentric exercise leads to the disappearance of the signs and symptoms associated with DOMS, which has been referred to as the repeated bout effect (RBE). Although the mechanisms underlying the RBE remain unclear, several mechanisms have been proposed, including the serial sarcomere number addition following exercise induced muscle damage. In the traditional DOMS and RBE protocols, muscle injury has been treated as a global parameter, with muscle force and strain assumed to be uniform throughout the muscle. To assess the effects of muscle-tendon unit strain, fiber strain, torque and injury on serial sarcomere number adaptations, three groups of New Zealand White (NZW) rabbits were subjected to chronic repetitive eccentric exercise bouts of the ankle dorsiflexors for 6 weeks. These eccentric exercise protocols consisted of identical muscle tendon unit (MTU) strain, but other mechanical factors were systematically altered. Following chronic eccentric exercise, serial sarcomere number adaptations were not identical between the three eccentric exercise protocols, and serial sarcomere number adaptations were not uniform across all regions of the muscle. Peak torque and relaxation fiber strain were the best predictors of serial sarcomere number across all three protocols. Therefore, MTU strain does not appear to be the primary cause for sarcomerogenesis, and differential adaptations within the muscle may be explained by the nonuniform architecture of the muscle, resulting in differential local fiber strains.

Extreme bone lengthening using distraction osteogenesis after trauma: a case report

We are reporting herein the result of a 22 cm tibial lengthening after using an acute shortening technique with acute temporary angulation for salvage of a posttraumatic lower limb injury. The patient was referred to our center 2 weeks after a Gustilo IIIB open complex injury to the lower limb that included bone and soft-tissue loss. After surgical debridement, the tibial gap was 22 cm and the soft-tissue defect on the anterior aspect of the calf measured 12 x 20 cm. An acute shortening using a 50 degrees angulation (apex posteriorly) of the tibia in an Ilizarov frame was done after a full assessment of all reconstructive surgical options. After complete wound healing, a progressive correction of the angulation was done. Bilevel tibial distraction at a rate of 1.75 mm/day restored the original lower limb length. The 22 cm tibial elongation included 17 cm proximal lengthening and 5 cm distal lengthening. The fractures consolidated after 371 days, all wounds had closed, and no signs of osteomyelitis were present. Good aesthetic and functional results were obtained. The patient had no leg discrepancy compared to his normal limb and he returned to his previous occupation as a garage mechanic and to his favorite sport, boxing. To our knowledge, this is the first report in the English literature of tibial lengthening of this magnitude following acute trauma.

Differential serial sarcomere number adaptations in knee extensor muscles of rats is contraction type dependent

Sarcomerogenesis, or the addition of sarcomeres in series within a fiber, has a profound impact on the performance of a muscle by increasing its contractile velocity and power. Sarcomerogenesis may provide a beneficial adaptation to prevent injury when a muscle consistently works at long lengths, accounting for the repeated-bout effect. The association between eccentric exercise, sarcomerogenesis and the repeated-bout effect has been proposed to depend on damage, where regeneration allows sarcomeres to work at shorter lengths for a given muscle-tendon unit length. To gain additional insight into this phenomenon, we measured fiber dynamics directly in the vastus lateralis (VL) muscle of rats during uphill and downhill walking, and we measured serial sarcomere number in the VL and vastus intermedius (VI) after chronic training on either a decline or incline grade. We found that the knee extensor muscles of uphill walking rats undergo repeated active concentric contractions, and therefore they suffer no contraction-induced injury. Conversely, the knee extensor muscles during downhill walking undergo repeated active eccentric contractions. Serial sarcomere numbers change differently for the uphill and downhill exercise groups, and for the VL and VI muscles. Short muscle lengths for uphill concentric-biased contractions result in a loss of serial sarcomeres, and long muscle lengths for downhill eccentric-biased contractions result in a gain of serial sarcomeres.