ABOS Part I Orthopedic Review: Duchenne Muscular Dystrophy & Chronic Exertional Compartment Syndrome | Part 22164

Correct Answer: D

The case describes a 7-year-old boy presenting with several classic early signs of Duchenne Muscular Dystrophy (DMD): frequent falls, difficulty climbing stairs, Gower's sign (using hands to push off thighs to stand), and calf pseudohypertrophy. These are all characteristic features seen in early to intermediate stages of DMD, typically between ages 5 and 10.

Significant thoracolumbar scoliosis (Cobb angle > 40°) is a major orthopedic complication of DMD, but it typically commences or rapidly progresses after the loss of ambulation, which usually occurs around ages 10-12. While the patient is experiencing increased falls and difficulty with higher-level motor skills, he is still ambulatory. Therefore, a severe scoliosis of this magnitude is less likely to be observed at age 7 compared to the other listed early signs.

Option A (Waddling gait): This is a characteristic broad-based, lordotic gait due to proximal muscle weakness, commonly seen in early DMD.

Option B (Gower's sign): This pathognomonic maneuver, where the child uses their hands to 'walk up' their legs to stand, is a direct compensation for weak quadriceps and hip extensors and is a key early indicator mentioned in the vignette.

Option C (Calf pseudohypertrophy): Enlargement of the calf muscles due to fatty and fibrous tissue infiltration is a classic early sign of DMD, also mentioned in the vignette.

Option E (Difficulty running and jumping): Early loss of higher-level gross motor skills like running and jumping is a common manifestation of progressive muscle weakness in DMD.

Correct Answer: B

The case explicitly states that pedicle screws are the preferred method of fixation in DMD patients due to their three-column purchase and superior biomechanical strength. This is particularly critical in the context of osteopenic bone, which is common in DMD due to chronic steroid use and reduced weight-bearing. The image provided illustrates a posterior spinal fusion construct utilizing pedicle screws and rods, consistent with this approach.

Option A (Hooks and wires are generally preferred over pedicle screws due to their flexibility in osteopenic bone): This is incorrect. Hooks and wires offer less rigid fixation and inferior pull-out strength compared to pedicle screws, making them less suitable for the osteopenic spines of DMD patients where robust fixation is paramount.

Option C (Cement augmentation of pedicle screws is contraindicated due to increased risk of neurological injury): This is incorrect. The case states that for severe osteopenia, cement augmentation of pedicle screws (e.g., polymethyl methacrylate) can be considered, although it adds complexity and risk. It is not an absolute contraindication but a technique used in challenging bone quality.

Option D (Spinal fusion in DMD typically involves short-segment constructs to preserve motion segments): This is incorrect. DMD scoliosis is typically a long C-shaped thoracolumbar curve, often requiring long fusions extending from the upper thoracic to the sacral or iliac region to achieve balance and stability, especially in non-ambulatory patients.

Option E (Iliac screws are rarely necessary, as pelvic obliquity can be adequately corrected with lumbar instrumentation alone): This is incorrect. The case states that iliac screws may be necessary to achieve stable pelvic fixation and correct pelvic obliquity, which is a common and significant component of spinal deformity in DMD.

Correct Answer: C

The case explicitly lists severe cardiorespiratory compromise as the most significant absolute contraindication to orthopedic surgery in DMD patients. Specifically, a severely impaired pulmonary function (e.g., FVC < 20% predicted, or significant CO2 retention) often precludes major surgery unless life-sustaining benefits clearly outweigh risks. A baseline FVC of 25% predicted with significant CO2 retention falls into this category, indicating severe respiratory compromise that would make elective surgery prohibitively risky.

Option A (Preoperative ejection fraction (EF) of 40%): While cardiac function is critical, an EF of 40% is generally considered moderate impairment. The case specifies an EF < 30-35% as a more definitive contraindication. An EF of 40% would require careful cardiac optimization but might not be an absolute contraindication on its own for an elective procedure like Achilles lengthening, which is less invasive than spinal fusion.

Option B (History of multiple low-energy long bone fractures): This indicates significant osteopenia, a common complication of DMD and corticosteroid use. While it increases surgical risk (e.g., for spinal instrumentation or fracture fixation), it is not an absolute contraindication for a soft tissue procedure like Achilles lengthening. Bone fragility is a relative contraindication, and management strategies exist.

Option D (Ongoing physical therapy and bracing for the contracture): Non-operative management is the cornerstone of DMD care. Ongoing PT and bracing indicate that conservative measures are being pursued, but if the contracture is severe and interfering with function (as implied by the need for surgery), this is not a contraindication but rather a preceding step to surgery.

Option E (Mild hip flexion contractures): Mild contractures are common in DMD and are often managed non-operatively or addressed in conjunction with other procedures. They do not represent an absolute contraindication to an Achilles lengthening.

Correct Answer: E

The case explicitly states that patients with DMD (and other myopathies) can experience a rhabdomyolysis-like syndrome in response to volatile anesthetics and depolarizing muscle relaxants. Therefore, succinylcholine, a depolarizing muscle relaxant, is absolutely contraindicated in DMD patients.

Option A (Total intravenous anesthesia (TIVA) with propofol): TIVA with propofol is often preferred in DMD patients as it avoids volatile agents and succinylcholine, mitigating the risk of rhabdomyolysis-like syndrome.

Option B (Non-depolarizing muscle relaxants (e.g., rocuronium)): Non-depolarizing muscle relaxants can be used, but their response may be altered in DMD patients, requiring careful monitoring and titration. They are not absolutely contraindicated like succinylcholine.

Option C (Volatile anesthetic agents (e.g., isoflurane)): Volatile agents are used with extreme caution or avoided in favor of TIVA due to the risk of rhabdomyolysis-like syndrome. While their use is discouraged or limited, succinylcholine is the absolute contraindication among the choices.

Option D (Regional anesthesia (e.g., epidural block)): Regional anesthesia techniques can be valuable for pain management in DMD patients and are not contraindicated, provided there are no other contraindications (e.g., coagulopathy).

Correct Answer: D

The case explicitly states that in DMD, the paraspinal musculature is profoundly atrophic and replaced by fatty and fibrous tissue. This significantly alters surgical planes, making subperiosteal dissection less distinct and potentially increasing intraoperative blood loss due to the highly vascularized fibrotic tissue. Anticipating this altered tissue characteristic is crucial for surgical planning and execution.

Option A (Hypertrophied paraspinal muscles requiring extensive dissection): This is incorrect. The paraspinal muscles are atrophic, not hypertrophied, in DMD.

Option B (Normal bone mineral density allowing standard pedicle screw placement): This is incorrect. The case highlights that chronic steroid use and reduced weight-bearing lead to significant osteopenia, which impacts pedicle screw fixation strength and increases the risk of vertebral body fracture. Standard pedicle screw placement may require augmentation or specialized techniques.

Option C (Highly distinct surgical planes facilitating subperiosteal dissection): This is incorrect. The replacement of muscle with fatty and fibrous tissue makes dissection planes less distinct, not highly distinct.

Option E (Minimal risk of intraoperative blood loss due to muscle atrophy): This is incorrect. The case specifically mentions that the fibrotic tissue replacing muscle can be highly vascularized, potentially increasing intraoperative blood loss, not minimizing it.

Correct Answer: C

The case emphasizes that for Achilles tendon lengthening, meticulous technique is required to avoid overcorrection or damage to neurovascular structures. Overcorrection leading to a calcaneus deformity must be avoided, as this can create new functional deficits. The image provided shows a lower limb, consistent with a procedure like Achilles tendon lengthening, where careful technique is paramount.

Option A (Aggressive overcorrection to prevent recurrence of the contracture): This is incorrect. The case specifically warns against overcorrection, stating it must be avoided as it can lead to new functional deficits (e.g., calcaneus deformity).

Option B (Complete tenotomy of the Achilles tendon without repair to maximize lengthening): This is incorrect. Achilles tendon lengthening is typically performed via sequential tenotomies (e.g., three-portal percutaneous technique for a Z-lengthening effect) or a formal open Z-plasty, which involves controlled lengthening, not a complete, unrepaired tenotomy.

Option D (Exclusive use of open Z-lengthening for all equinus contractures): This is incorrect. The case mentions both percutaneous Achilles tenotomy/lengthening (for its minimally invasive approach) and open Z-lengthening (for more severe or resistant contractures), indicating that the choice depends on the severity and specific situation.

Option E (Ignoring the sural nerve as it is not typically in close proximity to the Achilles tendon): This is incorrect. The case specifically mentions that during open Z-lengthening of the Achilles tendon, the sural nerve must be carefully mobilized and protected, indicating its proximity and vulnerability.

Correct Answer: C

The case clearly outlines the primary indications for spinal fusion in DMD. For a non-ambulatory patient with progressive scoliosis and declining pulmonary function, the main goals are to improve sitting balance, reduce pain, and preserve pulmonary function. The patient's FVC of 45% predicted, while reduced, is above the critical threshold (FVC < 20%) that would contraindicate surgery, making intervention timely to prevent further decline.

Option A (To restore ambulation and prevent further muscle weakness): This is incorrect. Spinal fusion does not restore ambulation in non-ambulatory DMD patients, nor does it prevent the underlying progressive muscle weakness. The goal is to manage the consequences of the weakness.

Option B (To prevent the development of hip and knee flexion contractures): This is incorrect. Spinal fusion addresses spinal deformity. Hip and knee contractures are managed with lower limb releases, stretching, and bracing, not spinal surgery.

Option D (To correct calf pseudohypertrophy and improve cosmetic appearance): This is incorrect. Calf pseudohypertrophy is a pathological sign of DMD and is not an indication for surgical correction. Cosmetic appearance is not a primary indication for major spinal surgery in DMD.

Option E (To address speech delay and cognitive dysfunction): This is incorrect. Speech delay and cognitive dysfunction are associated findings in DMD but are not musculoskeletal complications addressed by orthopedic surgery.

Correct Answer: C

The case highlights that chronic steroid use and reduced weight-bearing in DMD patients lead to significant osteopenia, which impacts pedicle screw fixation strength and increases the risk of vertebral body fracture during instrumentation. Therefore, a DEXA scan to assess bone mineral density is most crucial to guide implant selection (e.g., considering cement augmentation) and surgical technique for spinal instrumentation, ensuring adequate fixation in potentially fragile bone.

Option A (Electromyography (EMG) to assess muscle strength): EMG is used for diagnostic purposes and to assess muscle function, but it does not directly guide implant selection or surgical technique for spinal instrumentation in the context of bone quality.

Option B (Pulmonary function tests (PFTs) to determine respiratory reserve): PFTs are critical for assessing overall surgical risk and anesthetic planning, but they do not directly inform implant selection or technique related to bone quality.

Option D (Echocardiogram to evaluate cardiac ejection fraction): An echocardiogram is essential for assessing cardiac function and overall surgical risk, but it does not directly guide implant selection or technique related to bone quality.

Option E (Genetic testing to confirm dystrophin mutation): Genetic testing confirms the diagnosis of DMD but is not a preoperative assessment that guides implant selection or surgical technique for spinal instrumentation in the context of bone health.

Correct Answer: C

The case identifies respiratory insufficiency/failure as a moderate-to-high incidence early postoperative complication in DMD patients, especially after major surgery like spinal fusion. Symptoms like increasing shortness of breath, decreased oxygen saturation, and a weak cough are classic signs. The recommended management strategy includes prolonged mechanical ventilation (invasive/non-invasive), aggressive pulmonary hygiene, early mobilization, and respiratory consult.

Option A (Deep Vein Thrombosis (DVT); Initiate immediate systemic anticoagulation): DVT is a possible complication, but the symptoms described (shortness of breath, decreased O2 sat, weak cough) are more indicative of primary respiratory compromise rather than a DVT/PE as the initial event. While DVT prophylaxis is important, this is not the most likely immediate cause of these specific symptoms.

Option B (Wound infection; Administer broad-spectrum antibiotics and consider wound debridement): Wound infection is a possibility, but it typically presents with local signs (redness, warmth, drainage, fever) and usually manifests a few days later. The described symptoms are not typical for an early wound infection.

Option D (Cardiac decompensation; Optimize cardiac medications and transfer to ICU): Cardiac decompensation is a risk, but the symptoms (shortness of breath, decreased O2 sat, weak cough) are more directly related to pulmonary mechanics and respiratory muscle weakness, which are profoundly affected in DMD, especially post-spinal surgery. While cardiac monitoring is crucial, respiratory issues are often the more immediate and direct concern in this scenario.

Option E (Pseudarthrosis; Plan for revision surgery with additional bone graft): Pseudarthrosis (non-union) is a late postoperative complication, occurring months to years after surgery, not on postoperative day 2.

Correct Answer: C

The waddling gait (due to gluteus medius/minimus weakness) and Gower's sign (using hands to 'walk up' legs to stand) are classic early signs of Duchenne Muscular Dystrophy. Gower's sign specifically compensates for weakness in the quadriceps and hip extensors, which are crucial for standing up from a seated or prone position. The waddling gait is a result of proximal hip abductor weakness. Therefore, weakness in the proximal hip extensors and quadriceps is the primary underlying cause of these observed signs.

Option A (Distal forearm and hand intrinsic muscles): Weakness in these muscles is not characteristic of the early signs of DMD, which primarily affects proximal muscles.

Option B (Gastrocnemius-soleus complex): Weakness or contracture of the gastrocnemius-soleus complex leads to equinus deformity and toe-walking, but not directly to a waddling gait or Gower's sign.

Option D (Anterior tibialis and peroneal muscles): Weakness in these muscles would lead to foot drop or other ankle deformities, not the described gait or Gower's sign.

Option E (Shoulder abductors and external rotators): While shoulder girdle weakness can occur later in DMD, it is not the primary cause of a waddling gait or Gower's sign, which are lower limb and trunk-related compensatory mechanisms.

Correct Answer: C

The scenario describes a late postoperative complication (two years post-fusion) characterized by instrumentation failure (pedicle screw fracture, loss of correction) and increasing back pain. The case explicitly states that instrumentation failure (screw pullout, rod fracture) is a known late complication in DMD, with an incidence of 5-10%. The primary underlying cause for this in DMD patients is the significant osteopenia and poor bone quality, often exacerbated by chronic steroid use, which compromises implant purchase and strength.

Option A (Acute wound infection; Inadequate antibiotic prophylaxis): Acute wound infection is an early complication, typically presenting within weeks of surgery, not two years later. While late infections can occur, instrumentation failure is a more direct explanation for the described findings.

Option B (Deep Vein Thrombosis (DVT); Prolonged immobility): DVT is an early postoperative complication, usually occurring within weeks, not years, and presents with limb swelling or pulmonary symptoms, not instrumentation failure.

Option D (Adjacent segment disease; Excessive correction of the fused segment): Adjacent segment disease is a possibility, but the description of a fractured pedicle screw and loss of correction points more directly to instrumentation failure within the fused segment rather than pathology at an adjacent, unfused level.

Option E (Recurrence of lower limb contractures; Insufficient postoperative stretching): Recurrence of lower limb contractures is a complication of contracture release surgeries, not spinal fusion, and would present as limited range of motion in the limbs, not back pain and instrumentation failure.

Correct Answer: C

The correct answer is C. Chronic Exertional Compartment Syndrome (CECS) is characterized by pathologically non-compliant fascial envelopes that fail to accommodate the transient increase in muscle volume (up to 20%) during vigorous exercise. This leads to a precipitous rise in intracompartmental pressure, compromising microvascular perfusion and causing ischemic pain and nerve compression.

Option A describes acute compartment syndrome, which is typically traumatic and irreversible without immediate intervention. Option B describes Popliteal Artery Entrapment Syndrome, a vascular pathology involving dynamic arterial occlusion. Option D describes a tibial stress fracture, an osseous injury. Option E describes Medial Tibial Stress Syndrome, which involves diffuse inflammation along the posteromedial tibia, not primarily a fascial compliance issue.

Correct Answer: D

The correct answer is D. The Pedowitz criteria for diagnosing Chronic Exertional Compartment Syndrome state that one or more of the following pressure thresholds must be met: 1) A pre-exercise resting pressure greater than or equal to 15 mm Hg; 2) A one-minute post-exercise pressure greater than or equal to 30 mm Hg; 3) A five-minute post-exercise pressure greater than or equal to 20 mm Hg.

In this patient's right anterior compartment, all three readings individually meet these criteria: Resting (18 mm Hg ≥ 15 mm Hg), 1-minute post (45 mm Hg ≥ 30 mm Hg), and 5-minute post (32 mm Hg ≥ 20 mm Hg). Therefore, any one of these readings would be sufficient for diagnosis.

Correct Answer: C

The correct answer is C. Popliteal Artery Entrapment Syndrome (PAES) is a critical vascular differential diagnosis for exertional leg pain. In PAES, the popliteal artery is dynamically compressed, typically by the medial head of the gastrocnemius, during active plantarflexion or exercise. This leads to claudication-like symptoms and, importantly, diminished or absent pedal pulses (dorsalis pedis and posterior tibial) during or immediately after exercise. Chronic Exertional Compartment Syndrome primarily affects the microcirculation and capillary beds, and major arterial inflow is rarely compromised, thus distal pulses typically remain palpable post-exertion.

Options A, B, and D are musculoskeletal or neurological conditions that do not typically present with diminished distal pulses. Option E, Deep Vein Thrombosis, is a venous pathology and while it can cause leg pain and swelling, it is not typically exertional and does not cause diminished arterial pulses.

Correct Answer: C

The correct answer is C. The deep peroneal nerve innervates the muscles of the anterior compartment, including the tibialis anterior and extensor hallucis longus, which are responsible for ankle dorsiflexion and great toe extension, respectively. Ischemic neuropraxia of the deep peroneal nerve would therefore cause transient weakness (foot drop sensation) in these movements. The deep peroneal nerve also provides sensation to the first dorsal web space.

The superficial peroneal nerve provides sensation to the dorsum of the foot (excluding the first web space). Compression or ischemia of the superficial peroneal nerve would lead to the reported numbness and tingling along the dorsum of the foot. Both of these nerves are particularly vulnerable to compression in the anterior and lateral compartments, respectively, during episodes of elevated intracompartmental pressure.

The other options involve nerves with different motor and sensory distributions (e.g., sural nerve for lateral foot sensation, tibial nerve for plantarflexion and plantar foot sensation, femoral nerve for hip flexion and knee extension).

Correct Answer: C

The correct answer is C. The superficial peroneal nerve is the most critical nerve to identify and protect during an anterolateral fasciotomy. It typically pierces the deep fascia of the lateral compartment to become subcutaneous approximately 10-12 cm proximal to the lateral malleolus, often within the surgical field for a single-incision anterolateral approach. Injury to this nerve can result in permanent numbness over the dorsum of the foot and potentially neuropathic pain.

The deep peroneal nerve is located deeper within the anterior compartment and is generally protected by the muscle bellies during this approach, though care must be taken during the fascial release. The sural nerve is located more posteriorly and laterally, typically not in the primary field of an anterolateral approach. The saphenous nerve is a sensory branch of the femoral nerve, located medially. The tibial nerve is in the posterior compartment.

Correct Answer: D

The correct answer is D. While resting MRI is often normal in Chronic Exertional Compartment Syndrome (CECS), advanced imaging protocols utilizing post-exercise T2-weighted mapping can be highly suggestive of the condition. T2 hyperintensity within the affected compartments post-exercise reflects increased extracellular fluid and edema resulting from the compromised microcirculation and fluid extravasation, which is characteristic of CECS.

Option A suggests a stress fracture or periostitis. Option B suggests a stress fracture or Medial Tibial Stress Syndrome. Option C suggests Popliteal Artery Entrapment Syndrome. Option E suggests Deep Vein Thrombosis. None of these are primary findings for CECS, and the case explicitly states resting MRI was unremarkable, ruling out early stress fractures or MTSS.

Correct Answer: C

The correct answer is C. For high-demand competitive athletes, a partial fasciectomy (excision of a 1-2 cm strip of fascia) is often preferred over a simple fasciotomy. The primary rationale is to significantly reduce the risk of fascial re-approximation and subsequent recurrent compartmental hypertension. Simple fasciotomies, especially in the robust anterior compartment fascia, carry a higher risk of incomplete release or fascial scarring and re-tethering, leading to recurrence rates that can approach 15-20% in elite athletes. Excising a strip of fascia creates a larger, more permanent defect, minimizing this risk.

Option A is incorrect; a fasciectomy typically requires a slightly larger incision than a minimally invasive fasciotomy. Option B is incorrect; nerve injury risk is related to meticulous dissection, not the extent of fascial excision. Option D is incorrect; nerve identification is a separate step. Option E is incorrect; hematoma prevention is achieved through meticulous hemostasis, not the type of fascial release.

Correct Answer: B

The correct answer is B. In the immediate post-operative period (Phase 1), early active and passive range of motion exercises for the ankle and toes, particularly active dorsiflexion and plantarflexion, are critical to prevent the muscles from scarring down to the overlying subcutaneous tissues and skin. This helps maintain the mobility of the muscle bellies within the newly released compartment, preventing restrictive scar tissue formation that could lead to recurrent symptoms.

Option A is incorrect; rapid restoration of full muscle strength is a later goal. Option C is incorrect; the deep fascia is explicitly left open, so there is no fascial repair to assess for dehiscence. Option D is incorrect; the goal is to prevent scarring, not to stretch the fascia, which has been excised. Option E is a secondary benefit of early weight-bearing and movement, but the primary goal for specific muscle exercises is to prevent adhesions.

Correct Answer: C

The correct answer is C. Medial Tibial Stress Syndrome (MTSS) typically presents as a diffuse, dull ache along the posteromedial border of the distal third of the tibia. A key differentiating feature from CECS is its onset and offset characteristics: pain often occurs early in exercise, may warm up and improve during the activity, and then returns or worsens post-exercise, often with a prolonged ache at rest. Palpation reveals diffuse tenderness along the tibial crest, rather than tense muscle compartments.

Option A describes Popliteal Artery Entrapment Syndrome. Option B describes a Tibial Stress Fracture. Option D describes Superficial Peroneal Nerve Entrapment. Option E describes a more severe or persistent neurological deficit not typical of CECS's transient nature, or potentially a different neurological pathology. The case specifically highlights the differences in the comparative analysis table.

Correct Answer: C

The correct answer is C. The management algorithm for Chronic Exertional Compartment Syndrome (CECS) typically begins with conservative measures. However, in competitive athletes seeking to return to their prior level of performance, conservative measures have a notoriously high failure rate, often exceeding 80%. In this case, the patient has diligently trialed over six months of non-operative modalities without success, and the diagnosis has been definitively confirmed by intracompartmental pressure monitoring.

Given the failure of conservative treatment and the clear diagnosis, operative intervention (bilateral anterolateral fasciectomy, as indicated by the pressure readings) is strongly indicated and is the most appropriate next step to allow the patient to return to elite-level running.

Options A and B represent continued conservative management, which has already failed. Option D is unnecessary; intracompartmental pressure monitoring is the gold standard for diagnosis, and a post-exercise MRI is an adjunct, not a prerequisite for intervention after definitive pressure measurements. Option E is incorrect as Popliteal Artery Entrapment Syndrome has been clinically differentiated by the preservation of distal pulses and the specific pressure findings.

Duchenne Muscular Dystrophy is inherited in an X-linked recessive pattern. Dystrophin connects the cytoskeleton of a muscle fiber to the surrounding extracellular matrix through the cell membrane.

The Pedowitz criteria for chronic exertional compartment syndrome include a pre-exercise pressure >=15 mm Hg, a 1-minute post-exercise pressure >=30 mm Hg, or a 5-minute post-exercise pressure >=20 mm Hg.

Succinylcholine, a depolarizing muscle relaxant, is contraindicated in patients with DMD due to the risk of massive potassium release leading to fatal hyperkalemia and rhabdomyolysis.

The anterior compartment is most commonly affected in CECS. Compression of the deep peroneal nerve within this compartment can cause paresthesias in the first dorsal web space.

In non-ambulatory DMD patients, posterior spinal fusion to the pelvis is recommended for curves >20-30 degrees to maintain sitting balance and slow pulmonary decline. Bracing is generally ineffective and poorly tolerated.

Corticosteroids like deflazacort prolong independent ambulation, preserve pulmonary function, and delay the onset and progression of scoliosis in patients with DMD. However, they increase the risk of osteopenia and fractures.

The tibial nerve runs within the deep posterior compartment of the leg. Injury during deep posterior fasciotomy can result in numbness or paresthesias over the plantar aspect of the foot.

An FVC of less than 30% of predicted is generally considered a contraindication to spinal surgery in DMD due to the prohibitively high risk of postoperative ventilator dependence and respiratory failure.

The superficial peroneal nerve exits the lateral compartment fascia in the distal third of the leg. It is at high risk of iatrogenic injury during lateral compartment fasciotomy, leading to dorsal foot numbness.

In DMD, toe walking is initially a compensatory mechanism to keep the ground reaction force anterior to the knee. This locks the knee in extension and compensates for progressive quadriceps weakness.

The modified Pedowitz criteria for diagnosing CECS require one or more of the following: resting pressure ≥ 15 mmHg, 1 minute post-exercise pressure ≥ 30 mmHg, or 5 minutes post-exercise pressure ≥ 20 mmHg. A 1-minute post-exercise pressure of 30 mmHg or greater is highly diagnostic.

Dystrophin is a critical structural protein that stabilizes the sarcolemma by linking the intracellular actin cytoskeleton to the extracellular matrix through the dystrophin-associated glycoprotein complex. Its absence leads to membrane fragility, calcium influx, and eventual muscle necrosis.

The superficial peroneal nerve provides sensation to the dorsum of the foot (sparing the first web space) and is at high risk of injury during lateral and anterior compartment fasciotomies as it exits the fascia approximately 10-12 cm proximal to the lateral malleolus.

Scoliosis in DMD is progressive and does not respond to bracing. Surgical stabilization is typically recommended when curves exceed 20-30 degrees in non-ambulatory patients, usually involving posterior spinal fusion from the upper thoracic spine to the pelvis to correct pelvic obliquity.

Transitioning to a forefoot strike reduces the eccentric load on the tibialis anterior muscle during the initial contact phase of running. This modification has been shown to significantly lower anterior compartment pressures and alleviate CECS symptoms.

Patients with myopathies like DMD have upregulated extrajunctional acetylcholine receptors. The use of depolarizing neuromuscular blockers like succinylcholine causes massive potassium efflux from these receptors, leading to life-threatening hyperkalemia and cardiac arrest.

Popliteal artery entrapment syndrome (PAES) often mimics CECS but is characterized by vascular claudication. The pathognomonic sign is a decrease or loss of pedal pulses with active plantarflexion, which compresses the popliteal artery against an anomalous medial head of the gastrocnemius.

A 10-meter walk/run time greater than 9 seconds strongly predicts the loss of independent ambulation within 1 to 2 years in boys with DMD. Other indicators include the inability to rise from the floor or climb stairs.

The saphenous nerve travels with the greater saphenous vein along the medial aspect of the leg. It is highly susceptible to iatrogenic injury during a medial approach to the leg for releasing the deep posterior compartment.

Serum creatine phosphokinase (CPK) is profoundly elevated (often 10 to 100 times normal limits) in the early stages of Duchenne Muscular Dystrophy due to ongoing muscle membrane leakage and necrosis, well before significant muscle mass is lost.

The deep posterior compartment of the leg contains the tibialis posterior, flexor digitorum longus (FDL), and flexor hallucis longus (FHL). Failure to release the fascia over the tibialis posterior is a common cause of recurrent CECS.

Dilated cardiomyopathy is a hallmark of the advanced stages of Duchenne Muscular Dystrophy, resulting from dystrophin deficiency in cardiac muscle tissue, and is a leading cause of mortality in these patients.

Chronic Exertional Compartment Syndrome is bilateral in approximately 70-80% of cases, primarily because it is largely driven by anatomic predisposition and repetitive bilateral activities like running.

In advanced DMD, muscle imbalances predictably lead to upper extremity contractures characterized by shoulder adduction and internal rotation, elbow flexion, forearm pronation, and wrist/finger flexion.

According to the Pedowitz criteria, a resting intracompartmental pressure of ≥ 15 mmHg is sufficient to support the diagnosis of Chronic Exertional Compartment Syndrome.

Equinovarus contractures are the most common deformity in ambulatory boys with DMD. This is due to the relative sparing and overpull of the posterior tibialis muscle and Achilles tendon compared to the weaker dorsiflexors and evertors.

The most common reason for failed deep posterior compartment release is inadequate distally extending fasciotomy, specifically failing to release the fascial attachments of the soleus to the tibia (soleus bridge) and the fascial envelope of the tibialis posterior.

Corticosteroids (e.g., prednisone, deflazacort) are proven to prolong independent ambulation by an average of 2 to 3 years in DMD patients. They also delay the onset and reduce the severity of scoliosis, though they increase fracture risk due to osteopenia.

The Pedowitz criteria for diagnosing CECS require at least one of the following: resting pressure >15 mm Hg, 1-minute post-exercise pressure >30 mm Hg, or 5-minute post-exercise pressure >20 mm Hg. A 1-minute post-exercise pressure of 32 mm Hg meets these diagnostic criteria.

Succinylcholine is contraindicated in patients with myopathies like DMD due to the upregulation of extrajunctional acetylcholine receptors. Depolarization by succinylcholine leads to massive potassium efflux, resulting in life-threatening hyperkalemia and cardiac arrest.

Dystrophin is a vital structural protein that anchors the intracellular F-actin cytoskeleton to the extracellular matrix via the dystrophin-associated glycoprotein complex at the sarcolemma. Its absence makes the cell membrane highly susceptible to contraction-induced damage.

The superficial peroneal nerve runs in the lateral compartment and pierces the crural fascia in the distal third of the leg. It is at high risk of iatrogenic injury during anterior and lateral compartment fasciotomies.

In non-ambulatory DMD patients, scoliosis progresses rapidly and bracing is ineffective. Posterior spinal fusion to the pelvis is recommended for curves >20-30 degrees to prevent further progression, maintain sitting balance, and protect pulmonary function.

Transitioning from a rearfoot to a forefoot strike pattern reduces the eccentric load on the tibialis anterior during early stance. This gait modification has been proven to significantly lower anterior compartment pressures and relieve CECS symptoms.

The deep posterior compartment has the highest failure and recurrence rate following fasciotomy. This is often due to inadequate surgical release of the fascia overlying the tibialis posterior muscle.

In early DMD, patients develop a hyperlordotic posture to keep their center of gravity posterior to the hip joint. This mechanically compensates for progressive weakness of the gluteus maximus (hip extensors).

As pulmonary and cardiac care has improved, cardiopulmonary failure (specifically respiratory insufficiency and dilated cardiomyopathy) remains the leading cause of death in older DMD patients.

Popliteal artery entrapment syndrome can clinically mimic CECS. It is differentiated by diminished or absent pedal pulses during active plantarflexion or passive dorsiflexion, caused by the medial head of the gastrocnemius compressing the popliteal artery.

An FVC < 30% of predicted is widely considered a critical threshold in DMD. Patients below this level are at very high risk for prolonged or permanent postoperative mechanical ventilation after major spinal surgery.

Without dystrophin, the sarcolemma becomes fragile and leaky during muscle contraction. This allows a massive influx of extracellular calcium, which activates intracellular proteases (like calpains) and leads to myonecrosis.

In the early stages of DMD, ongoing muscle necrosis releases massive amounts of intracellular enzymes. Creatine kinase (CK) levels are characteristically elevated to 10-100 times normal values, often peaking before profound weakness appears.

The deep peroneal nerve runs within the anterior compartment of the leg. Elevated pressures in this compartment during exercise can compress the nerve, leading to paresthesias or numbness in its sensory distribution: the first dorsal web space.

Scoliosis in non-ambulatory DMD patients involves significant pelvic obliquity. Extending the fusion to the pelvis levels the spine over the pelvis, maintaining upright sitting balance and preventing pressure ulcers.

The tibialis posterior muscle is contained within its own distinct fascial sheath inside the deep posterior compartment. Failure to explicitly identify and release the epimysium/fascia of the tibialis posterior is the most common reason for surgical failure.

Corticosteroids (like deflazacort or prednisone) significantly preserve muscle strength in DMD. This prolongs the period of independent ambulation and notably delays both the onset and progression of scoliosis, though it does increase the risk of osteoporotic fractures.

DMD is caused by out-of-frame mutations leading to an almost total absence of dystrophin. BMD is caused by in-frame mutations, resulting in a shortened but partially functional dystrophin protein, yielding a milder phenotype.

Gowers' sign is a classic maneuver used to compensate for severe weakness in the proximal lower extremity musculature, particularly the gluteus maximus and quadriceps, which are needed for hip and knee extension during rising.

Under the Pedowitz criteria, an isolated resting intracompartmental pressure >15 mm Hg is considered diagnostic for Chronic Exertional Compartment Syndrome.

DMD is caused by an out-of-frame (frameshift) mutation in the dystrophin gene, resulting in absent or non-functional dystrophin. Becker MD is typically caused by an in-frame mutation resulting in a truncated but partially functional protein.

Pedowitz criteria for CECS include one or more of the following: resting pressure >= 15 mm Hg, 1-minute post-exercise pressure >= 30 mm Hg, or 5-minute post-exercise pressure >= 20 mm Hg.

Succinylcholine, a depolarizing neuromuscular blocker, is strictly contraindicated in patients with DMD due to the risk of severe rhabdomyolysis and life-threatening hyperkalemia, which can cause sudden cardiac arrest.

The superficial peroneal nerve is at high risk during fasciotomy of the lateral compartment. It provides sensation to the dorsum of the foot, while the deep peroneal nerve supplies the first web space.

In non-ambulatory patients with DMD, spinal fusion is typically recommended early, at a Cobb angle of 20-30 degrees. Early intervention ensures the surgery is performed before pulmonary function declines excessively.

The anterior compartment of the leg is the most frequently affected in chronic exertional compartment syndrome, often presenting with anterior pain, tightness, and occasionally transient foot drop.

An FVC of less than 30% of predicted is associated with a significantly higher risk of perioperative respiratory complications, prolonged intubation, and failure to wean from the ventilator.

The only consistently reliable non-operative treatment for CECS is cessation or modification of the inciting activity (e.g., stopping running). Orthotics, physical therapy, and NSAIDs are generally ineffective.

Dilated cardiomyopathy is nearly ubiquitous in patients with DMD by age 18 and is a leading cause of mortality alongside respiratory failure.

Popliteal artery entrapment syndrome presents with claudication-like symptoms in young athletes. A drop in ABI with active plantar flexion or passive dorsiflexion is characteristic, distinguishing it from CECS.

Corticosteroid therapy in DMD prolongs independent ambulation, preserves respiratory function, and decreases the incidence of severe scoliosis. However, it increases the risk of vertebral and long bone fragility fractures.

In chronic exertional compartment syndrome, pressures elevate to symptomatic levels during exertion but return to normal at rest without causing irreversible muscle necrosis, unlike the persistent ischemia seen in acute compartment syndrome.

Ambulatory DMD patients typically develop progressive hip flexion, knee flexion, and ankle equinus contractures. They compensate biomechanically with an increased lumbar lordosis and toe walking.

The deep posterior compartment contains the tibialis posterior, flexor digitorum longus, and flexor hallucis longus muscles. Surgical release requires precise division of the fascial compartments investing these specific muscles.

Elbow flexion contractures commonly develop in non-ambulatory DMD patients. These contractures can significantly interfere with functional tasks, feeding, and operating the joystick of a powered wheelchair.

Transitioning from a rearfoot (heel) strike to a forefoot strike pattern reduces the eccentric load on the anterior compartment musculature, potentially decreasing symptoms of anterior CECS.

In DMD, scoliosis fusions are typically extended to the pelvis to correct and prevent future pelvic obliquity. This is critical for maintaining a level, comfortable seated posture and distributing pressure evenly in a wheelchair.

The superficial peroneal nerve courses in the lateral compartment and exits the crural fascia or anterior intermuscular septum in the distal third of the leg. It must be meticulously identified and protected during the release.

Dystrophin is a vital structural protein that links the intracellular actin cytoskeleton to the transmembrane dystroglycan complex, stabilizing the sarcolemma against the extracellular matrix during repeated muscle contractions.