Eccentric Quadriceps Contractions Research Articles

Midsubstance Vastus Lateralis Tear in the Young Athlete: Case Report and a Review of the Literature.

Vastus lateralis tendon tear is an infrequent cause of lateral knee pain. Previously reported cases have described acute injury in middle-aged men after eccentric quadriceps contraction. This case report discusses 2 adolescent patients with longitudinal midsubstance tears diagnosed with MRI and dynamic ultrasound and treated successfully with operative intervention.

Hybrid Knot and Knotless Suture Anchor Repair for Patellar Tendon Rupture

Background: Patellar tendon ruptures are the third-most common injury involving the knee extensor mechanism. They typically occur in men under 40 years old as a result of eccentric quadriceps contraction while the knee is flexed and the foot is planted.1 The optimal treatment is surgical repair within 2 weeks of injury to prevent scar formation, degeneration, and loss of tendon excursion. Indications: Operative management is generally indicated for patellar tendon ruptures. In this case, a physically active, healthy 24-year-old man presented with acute pain, extensor lag, and patella alta related to a basketball injury. He was diagnosed with acute patellar tendon rupture/extensor mechanism disruption and indicated for surgery. Technique description: We describe a technique for primary patellar tendon repair which uses both knot-based and knotless suture anchor fixation. Using a pulley effect, sutures in the inferior patellar anchors are used to reduce and repair the patellar tendon back to its bony origin. Patellar anchor-based tapes and a suprapatellar traction suture are affixed with knotless anchors to the proximal tibia to reinforce the repair. Anchor-based suture limbs are used to repair the medial and lateral retinacula. Results: The senior authors’ experience with this technique has been excellent restoration of extensor mechanism function, with rehabilitation permitting early range of motion and no major complications or failures. This patient returned to unassisted activities of daily living between 8 and 12 weeks and had returned to gym workouts and recreational sports at 12 months. Discussion/conclusion: Biomechanical studies have demonstrated that compared with transosseous repair, suture anchor repair decreases gap formation and improves ultimate load to failure. Advantages of suture anchor repair include smaller incision, less tissue dissection, shorter operative time, and improved repair biomechanics. Our technique follows a principle of tendon repair using a high number of suture and tape limbs to span the repair. In addition, this technique incorporates a “double row” of suture anchors and spans the primary repair with a suture and tape “internal brace.” The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Mechanism of non-contact ACL injury: OREF Clinical Research Award 2021.

Anterior cruciate ligament (ACL) ruptures significantly impact athletes in terms of return to play and loss of long-term quality of life. Before the onset of this study, understanding the mechanism of ACL injury was limited. Thus, the primary focus of this manuscript is to describe our multi-faceted approach to uncovering the mechanism of noncontact ACL injury (NC-ACLI) with the goal of developing preventive strategies. The initial qualitative analysis of ACL injury events revealed most (70%) injuries involve minimal to no contact and occurr during landing or deceleration maneuvers in team sports with a minor perturbation before the injury that may disrupt the neuromuscular system leading to poor body dynamics. A series of quantitative videotape studies demonstrated differences in leg and trunk positions at the time of NC-ACLI in comparison to control subjects. Analysis of the faulty dynamics provoking NC-ACLI, especially the flat-footed landing component, supports the theory that an axial compressive force is the critical factor responsible for NC-ACLI. Our magnetic resonance imaging study demonstrated the NC-ACLI position was associated with a higher tibial slope, and joint contact occurring on the flat, anterior portion of the lateral femoral condyle versus the round, posterior aspect. Both anatomic conditions favor sliding (pivot shift) over rolling in the presence of an axial compressive force. Subsequent cadaveric studies supported axial compressive forces as the primary component of NC-ACLI. Both a strong eccentric quadriceps contraction and knee abduction moments may increase the compressive force at the joint thereby lowering the axial threshold to injury. This manuscript summarizes the NC-ACLI mechanism portion of the 2021 OREF Clinical Research Award.

Alterations in skeletal muscle repair in young adults with type 1 diabetes mellitus.

Though preclinical models of type 1 diabetes (T1D) exhibit impaired muscle regeneration, this has yet to be investigated in humans with T1D. Here, we investigated the impact of damaging exercise (eccentric quadriceps contractions) in 18 physically active young adults with and without T1D. Pre- and postexercise (48 h and 96 h), the participants provided blood samples, vastus lateralis biopsies, and performed maximal voluntary quadriceps contractions (MVCs). Skeletal muscle sarcolemmal integrity, extracellular matrix (ECM) content, and satellite cell (SC) content/proliferation were assessed by immunofluorescence. Transmission electron microscopy was used to quantify ultrastructural damage. MVC was comparable between T1D and controls before exercise. Postexercise, MVC was decreased in both groups, but subjects with T1D exhibited moderately lower strength recovery at both 48 h and 96 h. Serum creatine kinase, an indicator of muscle damage, was moderately higher in participants with T1D at rest and exhibited a small elevation 96 h postexercise. Participants with T1D showed lower SC content at all timepoints and demonstrated a moderate delay in SC proliferation after exercise. A greater number of myofibers exhibited sarcolemmal damage (disrupted dystrophin) and increased ECM (laminin) content in participants with T1D despite no differences between groups in ultrastructural damage as assessed by electron microscopy. Finally, transcriptomic analyses revealed dysregulated gene networks involving RNA translation and mitochondrial respiration, providing potential explanations for previous observations of mitochondrial dysfunction in similar cohorts with T1D. Our findings indicate that skeletal muscle in young adults with moderately controlled T1D is altered after damaging exercise, suggesting that longer recovery times following intense exercise may be necessary.

BILATERAL SENSORY DEFICITS AND WIDESPREAD HYPERALGESIA OCCUR FOLLOWING INDUCED DELAYED ONSET MUSCLE SORENESS OF THE QUADRICEPS

Unaccustomed eccentric exercise during sport or training may lead to delayed onset muscle soreness (DOMS), which has been demonstrated to influence postural control, potentially resulting in further injury. Afferent sensory input is critical to effective postural control, but little is known about somatosensory changes at the knee following induction of DOMS of the quadriceps muscle. The 'soreness' or hyperalgesia associated with DOMS has been postulated to occur because of damage to/inflammation of the exercised muscle, however, effects on central nociceptive mechanisms, which are known to induce altered postural responses, have been less studied. It was hypothesized that DOMS of the quadriceps muscle would result in widespread hyperalgesia and hypoesthesia at the knee. Therefore, the purpose of this study was to investigate the effects of DOMS on knee somatosensory changes in asymptomatic healthy participants. Quasi-experimental cohort study. Thirty participants (15 males and 15 females) took part in the study. Eccentric exercise consisted of 10 sets of 10 maximum eccentric quadriceps contractions performed with the dominant knee. Outcome measures consisted of pain intensity (Visual Analog Scale), pressure pain threshold (PPT), vibration perception threshold (VPT) and proprioception, measured via threshold to detection of passive motion (TDPM) at the knee, at three different assessment time points: (1) pre-eccentric exercise; (2) immediately and (3) 48 hours post-eccentric exercise. Not surprisingly, pain intensity increased and PPT of the vastus medialis and rectus femoris muscles decreased (hyperalgesia) immediately post-exercise on the exercised limb. However, at 48 hours, hyperalgesia was demonstrated at other lower extremity muscles, including bilaterally at the tibialis anterior muscles, and also at the hand. Evidence of hypoesthesia was also demonstrated. VPT and TDPM increased (worsened) ipsilaterally both immediately and 48 hours after exercise, and TDPM increased bilaterally at 48 hours. Females demonstrated greater impairment in TDPM than males at 48 hours. Expanding distribution of hyperalgesia, ipsilaterally impaired VPT and bilaterally impaired proprioception were demonstrated in the presence of DOMS. Inflammation from unaccustomed eccentric exercise may induce neuroplastic changes in nociceptive pathways resulting in wider distribution of pain and hypoesthesia. Futures studies examining the effect of DOMS related somatosensory changes on postural control may be warranted. 3.

Prolonged cooling with phase change material enhances recovery and does not affect the subsequent repeated bout effect following exercise.

The aim of this investigation was twofold: (1) to examine the effect of prolonged phase change material (PCM) cooling following eccentric exercise of the quadriceps on indices of muscle damage, and (2) to elucidate whether application of PCM cooling blunted the acute adaptive response to eccentric exercise, known as the repeated bout effect (RBE). Twenty-six males (25 ± 6years) performed an initial bout (B1) of 120 eccentric quadriceps contractions on each leg at 90% of their isometric strength and were then randomized to receive PCM packs frozen at 15°C (treatment) or melted packs (control) worn directly on the skin under shorts for 6h. The protocol was repeated 14days later (B2) with all participants receiving the control condition. PCM cooling provided protection against strength loss in B1 (P = 0.005) with no difference in strength between treatment groups in B2 (P = 0.172; bout by treatment by time P = 0.008). PCM cooling reduced soreness in B1 (P = 0.009) with no difference between treatment groups in B2 (P = 0.061). Soreness was overall lower following B2 than B1 (P < 0.001). CK was elevated in B1 (P < 0.0001) and reduced in B2 (P < 0.001) with no difference between treatments. The damage protocol did not elevate hsCRP in B1, with no difference between treatments or between bouts. This work provides further evidence that PCM cooling enhances recovery of strength and reduces soreness following eccentric exercise. Importantly, these data show for the first time that prolonged PCM cooling does not compromise the adaptive response associated with the RBE.

Update on Patellofemoral Anatomy and Biomechanics

The anatomy of the patellofemoral (PF) joint is reflective of its primary function of knee extension and eccentric quadriceps contraction, as it operates as a functional unit to optimize weight-bearing during knee range of motion. Our understanding of PF anatomy continues to evolve with the use of new dissection methods, as well as improving imaging modalities. A proper understanding of PF anatomy allows us to describe the morphological abnormalities that may predispose to PF pain and instability, such as trochlear dysplasia, excessive lateral tilt, bony malalignment, and patella alta. With an understanding of PF biomechanics, clinicians can improve treatment of these disorders through targeted operative and nonoperative treatment options. The goal of this review is to provide a functional anatomical overview pertinent to the operative treatment of PF disorders.

(108) Bilateral Sensory Deficits and Widespread Hyperalgesia following Delayed Onset Muscle Soreness of the Quadriceps

Unaccustomed eccentric exercise leads to delayed onset muscle soreness (DOMS). While DOMS has been demonstrated to result in altered postural control which may result in further injury, very little is known about the somatosensory changes at the knee in presence of DOMS of the quadriceps. DOMS elicited in this muscle was hypothesized to result in bilateral induced mechanical hyperalgesia, measured via pressure pain threshold (PPT) and hypoesthesia, evidenced by deficits in both vibration perception threshold (VPT) and proprioception which was measured via threshold to detection of passive motion (TDPM). Thirty participants (15 males and 15 females) took part in the study. Eccentric exercise consisted of 10 sets of 10 maximum eccentric quadriceps contractions of the dominant knee. Assessments consisted of pain intensity, PPT, VPT and, TDPM at 3 different assessment time points: (1) pre-eccentric exercise; (2) immediately and (3) 48 hours after eccentric exercise. Pain intensity increased and PPT decreased at 48 hours. VPT increased ipsilaterally both immediately and 48 hours after exercise. TDPM increased on the ipsilateral side immediately and bilaterally at 48 hours. Females demonstrated greater impairment in TDPM than males at 48 hours. Widespread hyperalgesia, ipsilaterally impaired VPT and bilaterally impaired proprioception were demonstrated in the presence of DOMS. Athletes performing strenuous lower limb eccentric exercise in training leading to DOMS may experience increased pain and hypoesthesia which may predispose them to lower quarter joint trauma. Unaccustomed eccentric exercise leads to delayed onset muscle soreness (DOMS). While DOMS has been demonstrated to result in altered postural control which may result in further injury, very little is known about the somatosensory changes at the knee in presence of DOMS of the quadriceps. DOMS elicited in this muscle was hypothesized to result in bilateral induced mechanical hyperalgesia, measured via pressure pain threshold (PPT) and hypoesthesia, evidenced by deficits in both vibration perception threshold (VPT) and proprioception which was measured via threshold to detection of passive motion (TDPM). Thirty participants (15 males and 15 females) took part in the study. Eccentric exercise consisted of 10 sets of 10 maximum eccentric quadriceps contractions of the dominant knee. Assessments consisted of pain intensity, PPT, VPT and, TDPM at 3 different assessment time points: (1) pre-eccentric exercise; (2) immediately and (3) 48 hours after eccentric exercise. Pain intensity increased and PPT decreased at 48 hours. VPT increased ipsilaterally both immediately and 48 hours after exercise. TDPM increased on the ipsilateral side immediately and bilaterally at 48 hours. Females demonstrated greater impairment in TDPM than males at 48 hours. Widespread hyperalgesia, ipsilaterally impaired VPT and bilaterally impaired proprioception were demonstrated in the presence of DOMS. Athletes performing strenuous lower limb eccentric exercise in training leading to DOMS may experience increased pain and hypoesthesia which may predispose them to lower quarter joint trauma.

Effect of Caffeine Supplementation on Quadriceps Performance After Eccentric Exercise

Green, MS, Martin, TD, and Corona, BT. Effect of caffeine supplementation on quadriceps performance after eccentric exercise. J Strength Cond Res 32(10): 2863-2871, 2018-Caffeine use is common among athletes seeking to capitalize on its potential ergogenic effects. Limited research has examined caffeine's effects when used after activities that resulted in exercise-induced muscle damage (EIMD). This study examined the effect of caffeine supplementation on uninjured and injured muscle. Eight men and women (N = 16) who were physically active individuals participated in this study (age: 24.3 ± 4.3 years; height: 173.0 ± 7.0 cm, mass: 75.2 ± 11.5 kg; body fat: 18.2 ± 15.9%). One leg was assessed under uninjured and injured (100 eccentric quadriceps contractions) conditions after caffeine supplementation (6 mg·kg), with the other leg assessed under both conditions after placebo supplementation. Compared with the placebo, caffeine increased peak isokinetic torque by 6.8 ± 2.3 and 9.4 ± 2.5% in uninjured and injured muscle, respectively, but had no effect on maximal voluntary isometric torque or fatigue index in uninjured or injured muscle, with treatments exhibiting similar (p > 0.05) alterations in isometric torque (-11.9 ± 2.2%), fatigue index (-13.9 ± 3.4%), and soreness (+44.0 ± 4.7) after eccentric contractions. The results of this study suggest that caffeine possesses a similar ergogenic effect on isokinetic torque in both uninjured and injured states, but no effect on the production of isometric torque, perception of soreness, or degree of relative fatigue. Athletes should consider the potential caffeine supplementation possesses during recovery from activities that resulted in EIMD.

The efficacy of cooling with phase change material for the treatment of exercise-induced muscle damage: pilot study

ABSTRACTPost-exercise cryotherapy treatments are typically short duration interventions. This study examined the efficacy of prolonged cooling using phase change material (PCM) on strength loss and pain after eccentric exercise. Eight adults performed 120 bilateral eccentric quadriceps contractions (90% MVC). Immediately afterwards, frozen PCM packs (15°C) were placed over the quadriceps, with room temperature PCM packs on the contralateral quadriceps. Skin temperature was recorded continually (6 h PCM application). Isometric quadriceps strength and soreness were assessed before, 24, 48, 72 and 96 h post-exercise. The protocol was repeated 5 months later, with room temperature PCM applied to both legs. There were three treatments: legs treated with 15°C PCM packs (direct cooling), legs treated with room temperature PCM packs contralateral to the 15°C PCM packs (systemic cooling), and legs tested 5 months later both treated with room temperature PCM packs (control). Skin temperature was 9°C–10°C lower with direct cooling versus systemic cooling and control (P < 0.01). Strength loss and soreness were less (P < 0.05) with direct cooling versus systemic cooling and control (strength 101%, 94%, 93%, respectively; pain 1.0, 2.3, 2.7, respectively). Six hours of PCM cooling was well tolerated and reduced strength loss and pain after damaging exercise.

Plasma Actin, Gelsolin and Orosomucoid Levels after Eccentric Exercise.

The present study investigated the acute effect of eccentric exercise on blood plasma actin, gelsolin (GSN) and orosomucoid (AGP) levels in untrained and moderately trained individuals, and their correlation with exercise induced muscle damage (EIMD) markers (CK, intensity of muscle soreness and maximal voluntary contraction torque deficit). Healthy physical education students (6 untrained, 12 moderately trained) participated in this research. Actin, GSN, AGP and CK levels were measured in blood plasma at baseline, immediately, 1 h, 6 h and 24 h post-exercise comprising 90 eccentric quadriceps contractions performed on a dynamometer. There was significant time main effect for GSN, AGP, CK and significant difference was found between baseline and the lowest value of post-exercise GSN (p < 0.05), as well as baseline and the highest value of post-exercise AGP (p < 0.05). Relationships were found between GSN levels and other indirect EIMD markers (between all GSN levels at post-exercise and CK activity at 6 h, p < 0.05; GSNMIN and muscle soreness at post-exercise, p < 0.04), GSN and AGP; however, actin did not correlate at any time points with GSN. Actin, GSN, AGP and CK responses after eccentric exercise do not seem sensitive to training status. The plasma actin level is used as an indicator of injury, however, our results suggest that it is not an accurate marker of EIMD, while plasma GSN concentrations show a better relationship with EIMD and the post-exercise inflammatory process. The elevated plasma AGP and the correlation between GSN and AGP seem to be promising for assessment of exercise-induced muscle injury.

Effects of elastic taping, non-elastic taping and static stretching on recovery after intensive eccentric exercise

ABSTRACTThe purpose of this study was to compare the effect of elastic tape (Kinesio tape) to placebo tape or static stretching on delayed onset muscle soreness. Fifty-one untrained female healthy volunteers were randomly assigned into three groups (n = 17/group), elastic tape, placebo tape and stretching group. Muscle soreness was induced by 4 sets of 25 maximal isokinetic (60°.s−1) eccentric contractions of dominant quadriceps on an isokinetic dynamometer. Compared with placebo tape, the elastic tape participants had less muscle soreness at 72 h post-exercise (p = 0.01). The elastic tape also increased isometric strength at 72 h post-exercise compared with the placebo (p = 0.03) and stretching group (p = 0.02). However, there was little effect between groups for changes in thigh circumference, jumping, pressure pain threshold, rate of perceived exertion, creatine kinase activity and joint motion. Elastic taping increased muscle strength recovery and reduced muscle soreness after intensive exercise.

The Efficacy of Cooling with Phase Change Material for the Treatment of Exercise-Induced Muscle Damage

PURPOSE: The limited efficacy of cold-water immersion in diminishing muscle damage may be due to inadequate treatment duration. Phase Change Material (PCM) can provide prolonged cooling. The purpose of this study was to examine the efficacy of post-exercise PCM cooling on strength loss and pain after eccentric exercise. METHODS: Four men and 2 women (39±13 yo) performed isometric quadriceps strength tests at 30°, 50° and 70° knee flexion, then performed 120 eccentric quadriceps contractions (Biodex System 2, Shirley NY) at 90% MVC. The protocol was repeated on the contralateral leg. PCM packs were then placed inside compression shorts over the quadriceps. PCM at 15°C were applied to the first leg, and PCM at room temperature were applied to the second leg. The 15°C packs were replaced after 3 hr (6 hr total). Quadriceps skin temperature was recorded continually. Strength and pain (VAS 0-10 scale) were assessed for 4 days. The protocol was repeated 5 mo later (room temperature PCM on both legs). Since cooling one leg might have a systemic effect on the contralateral leg, the effect of cooling was assessed by Treatment by Time ANOVA with treatments defined as Direct Cooling (leg with 15°C packs), Systemic Cooling (leg with room temperature packs contralateral to the 15°C packs), and Control (legs tested 5 mo later). RESULTS: Skin temperature averaged 21±1° C for Direct Cooling versus 31±2°C for Systemic Cooling and Control (P<0.01). Strength (% of baseline) across 4 days post-exercise was 101±9% for Direct Cooling, 94±16% for Systemic Cooling, and 91±7% for Control (Linear Treatment effect P<0.05). Peak strength loss occurred 1 day post exercise: Direct Cooling, 93±13%, Systemic Cooling, 92±16%, Control 83±10% (Linear Treatment effect P<0.01). Pain across 4 days post exercise was 0.9±1.0 for Direct Cooling, 1.6±1.4 for Systemic Cooling, and 2.5±2.4 for Control (Linear Treatment effect P<0.05). Peak pain occurred 2 days post exercise: Direct Cooling, 1.7±1.9, Systemic Cooling, 2.7±2.3, Control 4.0±0.7 (Linear Treatment effect P<0.05). CONCLUSIONS: Prolonged post-exercise muscle cooling using PCM resulted in minimal strength loss and pain compared to control (with a possible systemic effect also evident). This study demonstrates the potential utility of a cooling garment for accelerating recovery from damaging exercise.

Case report of a double spontaneous rupture: Quadriceps tendon and contralateral Achilles tendon

Uni- or bilateral quadriceps tendon ruptures are rare (1.37/100,000 person-years), those of the Achilles tendon are more common (21.5/100,000 person-years). To our knowledge, concomitant combination of these two ruptures has not been reported in the literature. This case reports a spontaneous rupture of quadriceps tendon and of Achilles contralateral tendon. 54 years, athletic patient without comorbidity, known for a ruptured left quadriceps tendon two years ago. During a ski descent, he presents a complete spontaneous rupture of the right quadriceps tendon and partial rupture of the left Achilles tendon, both repaired surgically. A stationary environment rehabilitation allowed a full recovery. Risk factors known in the literature for these tendon ruptures [1] , [2] (age, certain medications, anabolic steroids, certain systemic diseases, obesity, corticosteroid injections, static disorders in the knee or ankle, previous surgery) have not been found for this patient. The usually described triggers mechanisms could be found in this case (eccentric quadriceps contraction, sudden contraction of the sural triceps), occurring on tendons potentially weakened by repetitive microtrauma caused by intensive sport. However, this double spontaneous rupture and the previous rupture of the contralateral quadriceps tendon 2 years ago are suggestive of tendon abnormalities. In case of repetition, an histological analysis of the ruptured tendon could be achieved to assess the organization and structure of collagen fibers, tenocytes and microvascularization [3] . The search for a COL5A1 polymorphism also seems interesting because it has been associated with spontaneous tendon ruptures [3] , [4] .

Influence of pain on lower limb prosthesis use: implications on quality of life

compared to other groups (P 0.05). In sitting position at 60◦, 30◦, there were no statistically significant differences among each group (P> 0.05), while at 15◦ position there was a statistically significant difference in absolute error of angles under various tapings (P< 0.01), the absolute error of angles of KT group showed significant difference compared to other groups (P< 0.01). Conclusion(s): Kinesio taping may enhance the capacity of concentric, eccentric contractions of quadriceps and eccentric contractions of hamstring. KT can increase the muscle fibers recruitment capacity of vastus medialis and vastus lateralis and it may also improve the 15◦ knee joint position sense. Implications:Kinesio Taping is a physical therapy which is simple, safe and effective in preventing sports injury, worthy of our exploration and practice.

The Effects of Short-term Exercise Training on Peak-Torque Are Time- and Fiber-Type Dependent

We examined the susceptibility of fast and slow twitch muscle fibers in the quadriceps muscle to eccentric exercise-induced muscle damage. Nine healthy men (age: 22.5 ± 1.6 years) performed maximal eccentric quadriceps contractions at 120°·s-1 over a 120° of knee joint range of motion for 6 consecutive days. Biopsies were taken from the vastus lateralis muscle before repeated bouts of eccentric exercise on the third and seventh day. Immunohistochemical procedures were used to determine fiber composition and fibronectin activity. Creatine kinase (CK) and lactate dehydrogenase (LDH) were determined in serum. Average torque was calculated in each day for each subject. Relative to baseline, average torque decreased 37.4% till day 3 and increased 43.0% from the day 3 to day 6 (p < 0.001). Creatine kinase and LDH were 70.6 and 1.5 times higher on day 3 and 75.5 and 1.4 times higher on day 6. Fibronectin was found in fast fibers in subjects with high CK level on day 3 and 7 after exercise, but on day 7, fibronectin seemed in both slow and fast fibers except in muscles of 2 subjects with high fast fiber percentage. Peak torque and muscle fiber-type composition measured at baseline showed a strong positive association on day 3 (r = 0.76, p < 0.02) and strong negative association during recovery between day 3 and day 6 (r = -0.76, p < 0.02), and day 1 and day 6 (r = 0.84, p < 0.001). We conclude that the damage of fast fibers preceded the damage of slow fibers, and muscles with slow fiber dominance were more susceptible to repeated bouts of eccentric exercise than fast fiber dominance muscles. The data suggest that the responses to repeated bouts of eccentric exercise are fiber-type-dependent in the quadriceps muscle, which can be the basis for the design of individualized strength training protocols.

Operatively Treated Type IV Tibial Tubercle Apophyseal Fractures

Displaced tibial tubercle apophyseal fractures in children and adolescents are typically treated with closed reduction or open reduction with anterior to posterior screw fixation. Since the original classification by Watson-Jones and Ogden, an important variant with a posterior metaphyseal fracture line (type IV) was later described. However, there has been a lack of information regarding type IV tibial tubercle apophyseal fractures and its implications for surgical fixation. Twenty-four type IV tibial tubercle fractures in 23 children and adolescents were reviewed. Operative reports and clinic records were used to identify the patient demographics, fracture type, and clinical results. Available imaging was also used to characterize these fractures. Minimum follow-up was 2 years. Type IV fractures accounted for 18.5% (24/130) of all tibial tubercle apophyseal fractures. Three type IV fractures were identified that had an additional epiphyseal split. These were categorized as type IV-B, whereas the rest were considered type IV-A. There were 19 males and 4 females (average age, 14.8 y; range, 11.8 to 16 y). The most common mechanism was an eccentric quadriceps contraction during basketball. Three patients were initially treated with closed reduction and casting and were noted to have loss of reduction. All patients were treated definitively with open reduction and internal fixation or percutaneous screw placement. In addition to AP compression screws, 4 patients required supplemental plate fixation to stabilize the proximal tibia. Major complications included 1 compartment syndrome and 1 large DVT. All fractures healed and there were no growth disturbances. Type IV tibial tubercle apophyseal fractures are an important variant that requires careful assessment to ensure adequate stabilization of the proximal tibia when surgery is warranted. IV (prognostic case series).

Load-dependent variations in knee kinematics measured with dynamic MRI

Subtle changes in knee kinematics may substantially alter cartilage contact patterns and moment generating capacities of soft tissues. The objective of this study was to use dynamic magnetic resonance imaging (MRI) to measure the influence of the timing of quadriceps loading on in vivo tibiofemoral and patellofemoral kinematics. We tested the hypothesis that load-dependent changes in knee kinematics would alter both the finite helical axis of the tibiofemoral joint and the moment arm of the patellar tendon. Eight healthy young adults were positioned supine in a MRI-compatible device that could impose either elastic or inertial loads on the lower leg in response to cyclic knee flexion–extension. The elastic loading condition induced concentric quadriceps contractions with knee extension, while an inertial loading condition induced eccentric quadriceps contractions with knee flexion. Peak internal knee extension moments ranged from 23 to 33Nm, which is comparable to loadings seen in normal walking. We found that anterior tibia translation, superior patella glide, and anterior patella translation were reduced by an average of 5.1, 5.7 and 2.9mm when quadriceps loading coincided with knee flexion rather than knee extension. These kinematic variations induced a distal shift in the finite helical axis of the tibiofemoral joint and a reduction in the patellar tendon moment arm. We conclude that it may be important to consider such load-dependent changes in knee kinematics when using models to ascertain soft tissue and cartilage loading during functional tasks such as gait.

A Variable Impedance Knee Mechanism for Controlled Stance Flexion During Pathological Gait

A variable impedance knee mechanism (VIKM) has been developed as an orthotic intervention for individuals with weakened or paralyzed knee extensors. The purpose of the VIKM is to substitute for the function of eccentric quadriceps contraction to allow controlled levels of knee flexion during stance phase of gait and stair descent. The design concept, mechanism optimization, fabrication, bench testing, and initial results from walking tests with an able-bodied subject are reported. The VIKM utilizes a linear magnetorheological (MR) fluid damper with a four-bar linkage transmission to provide controllable resistance to knee motion. The design of the linkage enables the VIKM to provide large torques to resist motion at any knee angle. The prototype VIKM and full leg orthosis weigh 3.50 kg. The VIKM can provide a maximum of 64.5 N·m of torque in 35 ms. The average passive resistance is less than 4 N·m at an angular velocity of 210°/s. The ability of the VIKM to lock against knee flexion and allow knee motion under high loading is also demonstrated. Future work will focus on the development of a closed loop control system to automatically adjust the resistance level of the VIKM during walking and on clinical evaluation of the VIKM in pathological gait.

Can Arthroscopically Assisted Treatment of Chronic Patellar Tendinopathy Reduce Pain and Restore Function?

Patellar tendinopathy is a common source of pain in athletes, especially those involved in sports with a high incidence of jumping and cutting. Changes in training programs and exercises based on eccentric quadriceps contractions often relieve patients' symptoms. For athletes unresponsive to this treatment, some authors suggest open and arthroscopic procedures débriding either the tendon alone, or the tendon and bone. We asked whether an arthroscopically assisted approach to débride not only the tendon, bone, but also the peritenon could relieve pain and allow athletes to return to their former activities. We retrospectively reviewed 23 patients with a history of at least 6 months of painful patellar tendinopathy unresponsive to nonoperative treatment treated with an arthroscopic technique that débrided the tendon, inferior pole of the patella, and peritenon: 22 males and one female. Mean age was 29 years. Patients were evaluated using the anterior knee pain score of Kujala et al. The minimum followup was 12 months (mean, 58 months; range, 12-121 months). Twelve patients scored 100, one 99, one 98, five 97, two 94, one 90, and one 64. The Kujala et al. mean score was 96 (range, 64-100). All but four patients returned to their former sports activities. We observed no complications. Arthroscopic treatment can relieve the pain of refractory chronic patellar tendinopathy. Our observations were comparable with those previously reported for open techniques and a high percentage of patients returned to their previous activity level. Level IV, observational study. See Guidelines for Authors for a complete description of levels of evidence.