Category: Topics

Topics

Congenital Dislocation of the Knee

Definition

Congenital dislocation of the knee is a condition characterised by hyperextension deformity of knee with varying degrees of pathological anterior displacement of the tibia present at birth.

History

  • First described by Chenssier in 1812.
  • Subsequently reported by Chatelaine in 1822 and by Bord in 1834.

Aetiology

  • Three theories have been proposed about the causation. (Elmadag 2013)
    • Mechanical theory – Due to abnormal intrauterine position
    • Primary embryologic theory – Due to embryonic defect
    • Mesenchymal theory – Due to quadriceps contracture
  • The primary cause can be extrinsic or intrinsic.
  • Intrinsic causes are genetic or developmental and extrinsic factors are mechanical factors.
  • Extrinsic causes can be oligohydramnios, multiple pregnancy, intrauterine fetal malposition, quadriceps contracture and birth trauma.

Epidemiology

  • Majority of cases are sporadic.
  • Incidence is 1 in 100,000 live births. Seen in 1% of patients with DDH
  • Associations
    • Breech presentation – 30%
    • CTEV- 47%
    • DDH- 50%
    • Syndromes
      • Arthrogryposis multiplex
      • Larsen syndrome
      • Ehlers Danlos syndrome
      • Beals syndrome
      • Myelodysplasia

Classification

Leveuf and Pais Classification

Simple hyperextension – 15-200hyperextension, passive flexion up to 900.

Anterior subluxation – 25-400hyperextension and no flexion.

Anterior dislocation – No contact between distal femoral and proximal tibial articular surfaces.

Finder’s Classification (Finder 1964)

Type I– Physiological hyperextension up to 200is considered normal. Usually disappears by the age of 8 years.

Type 2– Simple hyperextension that persist into adult life.

Type 3– Anterior subluxation with hyperextension up to 900. Flexion only to neutral position.

Type 4– Dislocation of knee with anterior and proximal migration of proximal tibia.

Type 5– Complex variants associated with syndromes and other congenital deformities. 

Tarek CDK grading system (Tarek 2011)

G1– Simple recurvatum. Passive flexion >900. Manage by serial casting.

G2– Subluxation. Passive flexion 30-900. Manage by percutaneous quadriceps release

G3– Dislocation. Passive flexion <300. Manage by V-Y Quadricepsplasty.

Pathology

  • Quadriceps fibrosis and contracture.
  • Tight anterior capsule.
  • Hypoplastic or absent patella.
  • Hypoplastic suprapatellar bursa.
  • Anterior subluxation or dislocation of knee.
  • Transverse anterior skin crease.
  • Round condyles.
  • Increased tibial plateau.
  • Rotatory or valgus deformity of tibia.
  • Hamstrings may be displaced anteriorly and become extensors of knee.
  • Absent or elongated anterior cruciate ligaments (Katz 1967).
  • Lax or displaced cruciate ligaments.

Clinical features

  • Child born with varying degrees of hyperextension deformity of the knee.
  • Passive flexion of knee limited to varying degrees depending on the severity.
  • May be associated with other musculoskeletal anomalies like developmental dysplasia of hip or congenital talipes equinovarus.
  • Varying degrees of anterior displacement of the tibia in relation to the femur present.

Diagnosis

  • Prenatal ultrasound may help in diagnosis.
  • X-ray shows deformity with angulation in hyperextension type, anterior translation with variable amount of contact between femur and tibia in subluxation type and total loss of contact between femur and tibia with hyperextension deformity in dislocation type.
  • Ultrasound shows obliteration of  suprapatellar pouch.
  • Arthrogram may be necessary to identify intra-articular pathology.

How to treat these children?

When to treat?

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Topics

Acute Compartment Syndrome of the Leg
  • The muscles and neurovascular structures of limbs are separated into closed noncompliant osteofascial compartments by tough unyielding fascia that limit the ability for volume expansion. 
  • Blood supply to the structures within the compartment depends on the difference between the arterial and venous pressure (pressure gradient) and the local vascular resistance. 
  • Any decrease in the arterial pressure or increase in venous pressure reduces the pressure gradient. 
  • Increase in local vascular resistance decreases the blood flow.
  • When the blood flow cannot meet the metabolic demand of the tissues, first the function ceases, if not corrected the tissue undergoes necrosis.
  • Compartment syndrome develops when increase in the hydrostatic pressure within the compartment decreases the perfusion pressure, that results in cellular hypoxia, tissue ischemia, myoneural damage, muscle necrosis, permanent disability, loss of limb or even death. 
  • Acute compartment syndrome (ACS) is a dreaded complication of musculoskeletal injuries.

Epidemiology

  • Incidence is 3.1 per 100,000 population in the western world.
  • Male to female ratio is 10:1.
  • Age is the strongest factor with ACS being most common in the 2ndand 3rddecades.
  • Most common site is the leg, followed by the forearm.
  • ACS develops in 11.5% of tibial diaphyseal fractures.

History

  • First described by Richard von Volkmann in 1869 in the forearm. He described the sequelae and the causative factors in 1881.
  • Bardenheuer first described fasciotomy as treatment in 1906.
  • Rowland attributed raised intracompartmental pressure as the cause of ischemia and its sequelae.
  • Management of ACS first described by Petersen in 1888.
  • Myerson described compartment syndrome of the foot in 1987. (Myerson 1987)

Etiology

  • Cause may be fractures, soft tissue trauma, bleeding, extravasation or external compression.
  • Up to 30% of cases occur without fracture.
  • Causes may be divided into exogenous or endogenous.
  • Endogenous causes are hemorrhage, edema or perivascular infusions which increase in the volume of contents within the compartment.
  • Exogenous causes may be constricting casts, prolonged lithotomy positioning, drunken stupor, tight dressing etc.
  • Causes
    • Trauma
    • Thermal injuries
    • Constricting casts or dressings
    • Bleeding disorders including anticoagulant therapy
    • Nephrotic syndrome
    • Rhabdomyolysis
    • Accidental extravasation of infusions or drugs such as Propofol, Iohexol etc.
    • Lithotomy positioning during surgery
    • Streptococcal infections

Pathogenesis

  • Normal interstitial pressure is 8mm of mercury in adults and 10-15mm Hg in children.
  • Trauma leads to inflammation which leads to vasodilation and increased capillary permeability resulting in edema which increases interstitial pressure leading to increased venous capillary pressure. The decreased perfusion pressure leads to ischemia which causes further tissue damage creating a vicious cycle with positive feedback loop.
  • Ischemia leads to hypoxia and depletion of intracellular energy stores. Anaerobic metabolic pathways are activated to compensate leading to acidosis. Further reduction in the ATP production leads to shut down of sodium-potassium ATPase channels that maintain the cellular polarity and osmotic balance. Loss of cellular polarity leads to influx of chloride ions and cellular swelling. Increased cytosolic calcium accumulation causes lysosomal enzyme release and cell lysis.
  • Cell lysis releases intracellular toxins, leading to microvascular damage, inflammation, increased capillary permeability, capillary leakage and increased intra-compartmental pressure. 
  • Ischemia of one hour can lead to neuropraxia and axonotmesis can start developing by 4 hours. Irreversible changes start appearing by 6 hours.
  • Edema is due to increased capillary permeability secondary to injury or reperfusion.

Vicious Cycle of pathogenesis

Clinical Features

  • Compartment syndrome should be suspected in awake patients with unrelenting and increasing pain not responding to standard dose of analgesics, pain on passive stretch, paresthesia and paresis.
  • Classically the symptoms are described as 5 P’s. 
    • Pain
    • Pallor
    • Pulselessness
    • Paresis
    • Paresthesia
  • Griffiths described the 4 P’s in 1948; pain, pain on stretch, paresthesia and paresis (Griffiths 1948). Pulselessness and pallor were added later.
  • The classically described pulselessness is absent as the systolic blood pressure usually remains above the compartment pressure even in the late stages.
  • Pain which is persistent and increasing is the earliest and most common sign.
  • Pain on passive stretching of involved muscles is the most sensitive sign.
  • In the leg, anterior compartment is most commonly involved followed by the lateral compartment.
  • In children, the presentation is by 3 A’s
    • Anxiety
    • Agitation
    • Analgesic need that continuously rises
  • Compartment syndrome should be ruled out in unconscious patients with persistent tachycardia if there is no other cause or hypotension.
  • Risk factors that increase the likelihood of ACS are high velocity injury, systemic hypotension, younger age and obtunded patients.
  • Multiple injury patients with hypotension and hypoxia are more susceptible to compartment syndrome.
  • Other injuries more susceptible to compartment syndrome are vascular injuries with peripheral ischemia, high velocity injuries, crush injuries, and comminuted proximal tibial fractures.
  • Patients on anticoagulants are at high risk of ACS after injury.
  • More common in the young due to relatively thick and inelastic fascia.
  • Age between 12-29 years is the strongest predictor for ACS. 
  • Fractures of the tibia and fibula are 4 times more likely develop in comparison to all other fractures.
  • 36% of cases are due to tibial shaft fractures followed by soft tissue injury (23%), distal end radius #s (10%), forearm diaphyseal #s (8%) and crush syndrome (8%). (McQueen 2000)

Diagnosis

  • Diagnosis may be made by clinical examination or by measurement of compartment pressure or tissue oxygenation.
  • Diagnosis is unconscious patients’ needs compartment pressure monitoring.
  • Compartment pressure measurement by infusion technique was described by Whitesides in 1974 (Whitesides 1974). 
  • Compartment pressure measurement techniques
    • Whitesides infusion technique
    • Matsen’s continuous infusion and monitoring technique
    • Mubarak wick catheter technique
    • Stick technique
    • Fine wire transducer technique
    • Weiner fibro-optic transducer tip catheter technique
  • Some of the available catheters are the following
    • Slit catheter
    • Solid-state transducer intra-compartmental catheter (STIC)
    • Transducer tipped catheter
    • 18G needle with arterial-line transducer
  • Arterial line transducers with side-port needles, slit catheters and self contained measuring systems are most accurate. (Keudell 2015)
  • Monitoring of ICP by slit catheter technique has a sensitivity of 94% and specificity of 98% when pressure gradient (∆P) of 30mm Hg is used for diagnosis.

Compartment Pressure Measuring Technique

  • Compartment pressure should be measured within 5 cm of the fracture and pressure within all 4 compartments of the leg should be measured. 
  • Proper technique which includes proper positioning of the catheter within the compartment, proper setup of devices, proper zeroing is essential for correct measurement of intra-compartmental pressure. Otherwise catastrophic errors are likely. 
  • The landmarks for insertion of needle for compartment pressure measurement are as follows.
    • Superficial posterior compartment- In the posterior midline of calf.
    • Deep posterior compartment- 1 cm posterior to posteromedial border of tibia.
    • Anterior compartment- 2 cm lateral to the tibial crest.
    • Lateral compartment- Directly over the fibula.
  • Diagnosis is made if the difference between compartment pressure and diastolic pressure (∆P) is less than 30mm (McQueen 1996) or if the intra-compartmental pressure is above 30mm of Hg (Whitesides 1975).
  • Recently 35% false positive rate was reported when compartmental pulse pressure of <30mm Hg on single measurement was used in patients with acute fractures with no clinical evidence of compartment syndrome. (Whitney 2014)

Treatment

  • Timely diagnosis and dermatofasciotomy is essential to ensure optimum outcomes.
  • Initial treatment consists of removal of circumferential dressings and elevation of the limb to the level of heart.
  • The limb should not be elevated in impending compartment syndrome as it further reduces pressure gradient.
  • Techniques of fasciotomy
    • Dermatofasciotomy
    • Percutaneous fasciotomy
  • Percutaneous fasciotomy is contraindicated in trauma patients
  • Techniques of dermatofasciotomy
    • Mubarak’s 2-incision, 4-compartment fasciotomy
    • Matsen’s parafibular 4-compartment fasciotomy
    • Fibulectomy-fasciotomy
  • Fibulectomy-fasciotomy is contraindicated in trauma patients.
  • Mubarak’s 2-incision, 4-compartment fasciotomy of leg
    • Medial incision for release of deep and superficial posterior compartments made 2 cm posterior to the posteromedial border of tibia. Incise from proximal tibia to the musculotendinous junction of Achilles tendon. Protect saphenous nerve and vein. Incise fascia to release superficial posterior compartment. Elevate the soleus from the medial border of tibia to expose the deep posterior compartment and release the fascia.
    • Lateral incision for release of anterior and lateral compartments made 2 cm anterior to the fibular head. Incise from fibular head to the distal fibula Protect superficial peroneal nerve distally. Elevate the anterior flap. Incise fascia to release anterior compartment anterior to the anterior intermuscular septum. Elevate the posterior flap, incise the fascia along the posterior border of fibula to release the lateral compartment.
  • Matsen’s parafibular dermatofasciotomy.
  • After fasciotomy, the viability of the muscle should be ascertained by the 4 C’s: Color, Consistency, Contractility and Capacity to bleed.
  • The wound left open and spring sutures placed to progressively close the wound.
  • Patient returned to operation theatre at 48 hours to reassess the wound. 
  • Fasciotomy increases the duration of hospital stay, escalates the costs, increases the chance of infection and interferes with fracture healing.
  • Recently the need for release of all four compartments in all patients have been questioned and an algorithmic approach consisting of selective release of compartments have been put forward. (Tornetta 2016)
  • Tornetta 2016 algorithm advises measurement of diastolic BP preoperatively, measurement of ICP, fasciotomy of anterior and lateral compartments, measurement of ICP of posterior compartments and medial incision if the pressure difference with diastolic BP (∆P) is less than 30mm Hg and to avoid release if ∆P is more than 30mm Hg. Close post-operative monitoring by clinical examination every 2 hours is necessary. They did not recommend this algorithm in centres with no facility to monitor the intracompartmental pressure in the post-operative period. 

Complications

  • Delayed or missed diagnosis may lead to complications such as renal failure, ischemic contractures and limb loss.
  • Cause of delayed or missed diagnosis
    • Unconscious or inebriated patients
    • Regional or general anesthesia
    • Polytrauma
    • Soft tissue injuries
    • Inexperience
    • Over-reliance on clinical symptoms and signs
  • Complications of delayed or missed diagnosis
    • Muscle necrosis and contractures
    • Permanent neurological deficit
    • Infection
    • Chronic pain
    • Amputation
    • Death
  • The side effects or complications of fasciotomy are muscle weakness, chronic venous insufficiency, adherent scars, impaired sensation, ulceration, increases in duration of hospitalization and costs and the delay in definitive treatment.

Recent Advances

  • Newer diagnostic tools include the following.
    • Near-infrared spectroscopy (NIRS) uses differential light reflection and absorption characteristics to estimate the proportion of hemoglobin saturated with oxygen 2-3 cm below the skin. It is currently FDA approved for noninvasive continuous monitoring of pressure in the intracranial and somatic tissues. Skin pigmentation and thickness of subcutaneous fat may interfere with NIRS. 
    • Radio-frequency identification implants are minimally invasive devices with sensors to measure pressure, oxygenation etc. that are microfabricated into silicon substrate.  It uses RFID technology to transmit the data collected.
  • Newer methods to reduce pressure
    • Methods to decrease intramuscular pressure
      • Anti-inflammatory drugs like indomethacin
      • Ultrafiltration catheters as treatment- Tissue ultrafiltration by insertion of small diameter hollow fibers into the compartment, connected to suction to remove interstitial fluid to reduce compartment pressure.
      • Foot pumps
      • Mannitol
      • Diuretics
      • Decompression by dorsal skin fenestration or pie crusting in compartment syndrome of foot.
    • Improving tissue oxygenation
    • Free radical scavengers 
    • Small-volume resuscitation with hypertonic saline.

References

  1. von Keudell AG, Weaver MJ, Appleton PT, et al. Diagnosis and treatment of acute extremity compartment syndrome. Lancet. 2015;386:1299–1310.
  2. McQueen MM, Duckworth AD, Aitken SA, et al. The estimated sensitivity and specificity of compartment pressure monitoring for acute compartment syndrome. J Bone Joint Surg Am. 2013;95:673–677. 
  3. Sanjit R. Konda, Benjamin S. Kester, Nina Fisher, BS, Omar A. Behery, Alexander M. Crespo, Kenneth A. Egol. Acute Compartment Syndrome of the Leg. J Orthop Trauma 2017;31:S17–S18. 
  4. Whitesides TE, Heckman MM. Acute compartment syndrome: update on diagnosis and treatment. J Am Acad Orthop Surg. 1996;4:209–218.
  5. Manjoo A, Sanders D, Lawendy A, et al. Indomethacin reduces cell damage: shedding new light on compartment syndrome. J Orthop Trauma. 2010;24:526–529.
  6. Bariteau JT, Beutel BG, Kamal R, et al. The use of near-infrared spectrometry for the diagnosis of lower-extremity compartment syndrome. Orthopedics. 2011;34:178.
  7. Volkmann R: Die Krankheiten der Bewegungsorgane [Diseases of the musculoskeletal system], in von Pitha FR, Billroth T, eds: Handbuch der allgemeinen und speziellen Chirurgie. Stuttgart, Germany: Ferdinand Enke, 1865, vol 2, pp 234–920.
  8. Volkmann R: Krankenheiten der Bewegungsorgane. In Pitha, Billroth (eds): Handbuch der Chirurgie, Erlangen, 1869:846.
  9. Volkmann R: Die ischaemischen Muskellahmungen and Kontrakturen, Zentralb Chir 8:801-803, 1881.
  10. Bardenheuer L: Die ischamische Kontraktur und Gangran als Folge der Arterienverletzung, Leuthold’s Gedenkscrift 2:87, 1906.
  11. Rowland SRP: Volkmann’s contracture, Guys Hosp Gaz 24:87, 1910.
  12. Whitesides TE, Haney TC, Morimoto K, Harada H: Tissue pressure measurements as a determinant for the need of fasciotomy. Clin Orthop Relat Res 1975;113:43-51.
  13. McQueen MM, Court-Brown CM: Compartment monitoring in tibial fractures. The pressure threshold for decompression. J Bone Joint Surg Br 1996;78(1):99-104.
  14. Whitney A, O’Toole RV, Hui E, et al: Do one-time intracompartmental pressure measurements have a high false-positive rate in diagnosing compartment syndrome? J Trauma Acute Care Surg 2014;76(2):479-483.
  15. Paul Tornetta III, Brian L Puskas, Kevin Wang. Compartment syndrome of the leg associated with fracture: An algorithm to avoid releasing the posterior compartments. 
  16. Arvind G von Keudell, Michael J Weaver, Paul T Appelton, Donald S Bae, George S M Dyer, Marilyn Heng, Jesse B Jupiter, Mark S Vrahas. Diagnosis and treatment of acute extremity compartment syndrome. Lancet 2015; 386: 1299–1310.
  17. McQueen MM, Gaston P, Court-Brown CM. Acute compartment syndrome. Who is at risk? J Bone Joint Surg Br 2000; 82: 200–03.
  18. Myerson M. Acute compartment syndromes of the foot. Bull Hosp Jt Dis Orthop Inst. 1987;47:251–261.
  19. Griffiths DL. The management of acute circulatory failure in an injured limb. J Bone Joint Surg Br. 1948;30:280–298.
  20. Cascio BM, Wilckens JH, Ain MC, Toulson C, Frassica FJ. Documentation of acute compartment syndrome at an academic health-care center. J Bone Joint Surg Am. 2005;87:346–350.
  21. Whitesides TE, Jr., Haney TC, Harada H, Holmes HE, Morimoto K. A simple method for tissue pressure determination. Arch Surg. 1975;110:1311–1313.
  22. Matsen FA 3rd: Compartmental Syndromes, Orlando, Fla, Grune & Stratton, 1980. 
  23. Mubarak SJ, Hargens AR, Owen CA, et al: The wick catheter technique for measurement of intramuscular pressure: a new research and clinical tool, J Bone Joint Surg Am 58:1016-1020, 1976. 
  24. Weiner G, Styf J, Gershuni D: Effect of ankle position and a plaster cast on intramuscular pressure in the human leg, J Bone Joint Surg Am 76:1476-1482, 1994.

Further Reading

  1. Crespo AM, Manoli A III, Konda SR, Egol KA: Development of Compartment Syndrome Negatively Impacts Length of Stay and Cost After Tibia Fracture. J Orthop Trauma 2015;29(7):312-315.
  2. O’Toole RV, Whitney A, Merchant N, et al: Variation in diagnosis of compartment syndrome by surgeons treating tibial shaft fractures. J Trauma 2009;67(4):735-741.
  3. Boody AR, Wongworawat MD: Accuracy in the measurement of compartment pressures: A comparison of three commonly used devices. J Bone Joint Surg Am 2005;87(11):2415-2422.
  4. Large TM, Agel J, Holtzman DJ, Benirschke SK, Krieg JC: Interobserver variability in the measurement of lower leg compartment pressures. J Orthop Trauma 2015;29(7):316-321.
  5. Tharakan SJ, Subotic U, Kalisch M, Staubli G, Weber DM: Compartment pressures in children with normal and fractured forearms: A preliminary report. J Pediatr Orthop 2015.
  6. Mubarak SJ, Owen CA: Double-incision fasciotomy of the leg for decompression in compartment syndromes. J Bone Joint Surg Am 1977;59(2):184-187.
  7. Poon H, Le Cocq H, Mountain AJ, Sargeant ID: Dermal fenestration with negative pressure wound therapy: A new technique for managing soft tissue injuries associated with high-energy complex foot fractures. J Foot Ankle Surg 2016;55(1):161-165.
  8. Odland RM, Schmidt AH: Compartment syndrome ultrafiltration catheters: Report of a clinical pilot study of a novel method for managing patients at risk of compartment syndrome. J Orthop Trauma 2011;25(6):358-365.
Topics

Legg Calve Perthes Disease

Legg Calve Perthes disease (LCPD) is a self-limiting condition caused by temporary interruption of blood supply to the growing proximal femoral epiphysis leading to necrosis, collapse and revascularization. Though the cause of vascular occlusion is not yet known, it leads to morphological and developmental changes in the proximal femoral head, femoral neck and acetabulum. The resultant irreversible deformation of femoral head, growth retardation, shortening of femoral neck, coxa vara and joint subluxation results in articular incongruity, altered joint mechanics predisposing the hip to premature osteoarthritis.

History

1905-         Kohler described radiographic changes of a patient similar to LCPD

1909-         Henning Waldenström described it as a benign form of tuberculosis.

1909-         Independently described by Arthur Thornton Legg from USA, Jacques Calve from France and George Perthes from Germany. 

1921-         Phemister described histologic findings suggestive of osteonecrosis in the specimens of a patient treated by curettage. He described creeping substitution during reconstitution phase.

1926-         Konjetzny first showed interruption of vascular supply.

1952-         Varus containment osteotomy described by Soeure of Belgium.

1962-         Salter described innominate osteotomy.

Epidemiology

Reported incidence range from 0.2 to 19.8 per 100000 population per year. Age of presentation of active disease range from 2 years to 11 years, but most commonly occur between 4-8 years of age. Boys are 4-5 times more commonly affected than girls. 10-15% of cases have involvement of opposite hip either simultaneously or at a later age. Boys 5 times more commonly affected than girls. Bilateral involvement is more common in girls.

Aetiology

Vascular occlusion leading to osteonecrosis in the growing epiphysis is the pathophysiologic pathway of LCPD. LCPD results from repeated episodes of vascular occlusion and hypercoagulable states may play a role in the pathogenesis. Vascular occlusion may be extrinsic or intraluminal. Vascular occlusion may be arterial or venous. Veins of proximal femur are susceptible to occlusion because of very thin walls, low flow rates, tortuous course around arteries and low pressure. Venous occlusion can lead to increased intraosseous pressure, reduced arterial blood flow, hypoxia and ischemic necrosis.

The exact cause of occlusion is not yet identified. The proposed mechanisms include trauma, genetic mutations, hypercoagulable states and transient synovitis. 

Higher incidence of factor V Leiden mutation, protein S deficiency, elevated factor VIII, and prothrombin G20210A mutation are reported especially in males. These conditions may result in thrombophilia or hypofibrinolysis. Multifactorial origin acting through a single shared common pathway is the currently favored model. Recently a single missense mutation of COL2A1 gene for type II collagen leading to replacement of glycine with serine at the codon 1170 have been reported in Asian families with multiple affected members.

A recent study reported coagulation anomalies in 75% of cases. The anomalies were protein C deficiency, protein S deficiency, elevated lipoprotein A and hypofibrinolysis. Other studies failed to demonstrate a similar finding.

Pathogenesis

Vascular occlusion leads to ischaemic necrosis. Ischaemic necrosis has biological and mechanical effects. Biologic consequence is a period of softness of head making it vulnerable for deformation and cessation of epiphyseal growth. Growth arrest can lead to femoral neck shortening and coxa vara. Greater trochanteric overgrowth of varying severity is seen in over 90% of patients with LCPD which can lead to Trendelenburg limp. Mechanical weakening leads to collapse due to repeated mechanical stresses. Mechanical effects are due to lose of sphericity of femoral head.

Biological effects are due to vascular compromise leading to cell death, followed by vascular ingrowth and bone resorption, finally ending with new bone deposition. Mechanical effects are due to softening, subchondral fracture, collapse, loss of sphericity, lateral extrusion, superolateral hinging, labral tear, stress concentration, articular cartilage degeneration and osteoarthritis. 

Ischaemic damage is followed by invasion of dead trabeculae by neovascularization, removal of dead trabeculae by osteoclasts followed by reossification by creeping substitution or repair by fibrovascular tissue which leads to weakening of femoral Head. Weakened femoral head collapses leading to flattening and deformation of head. Superolateral part of deformed head gets extruded outside the confines of acetabulum. Progressive deformation leads to lateral subluxation, articular incongruity and impingement. Altered joint forces leads to early arthritis in adulthood. 

The disease process evolves through the stages of avascular necrosis, fragmentation, reconstitution and healing. Extrusion of femoral head is the most important factor in deformation of femoral head. It occurs during the latter part of fragmentation stage. The final outcome is coxa magna (enlarged head and neck), coxa breva (shortened neck) and coxa plana (flattened head) with femoroacetabular impingement.

Associations

LCPD is associated with delayed skeletal age and low birth weight. Cranial structures are relatively spared from growth retardation than caudal structures with the foot showing greatest growth retardation. Low socioeconomic status is a strong association pointing towards environmental factors. Low concordance in identical twins is an evidence against genetic factors. Inguinal hernia, genitourinary malformations, undescended testes are reported associations. 

Clinical Features

Patients may present in childhood, adolescence or in adulthood. Usually asymptomatic initially till collapse or subchondral fracture develops. Child presents with painless limp and later complains groin pain or knee pain. Groin pain and lateral hip pain are the most common presentations. Lateral pain may be due to abductor insufficiency, trochanteric bursitis or trochanteric impingement. Groin pain may be due to impingement, instability or arthritic changes. Posterior pain is usually due to impingement.  

Gait may be antalgic or Trendelenburg type. Lumbar lordosis may be exaggerated due to flexion deformity. Anterior superior iliac spine may be at a higher level in presence of adduction deformity. There may be wasting of thigh and gluteal muscles. Tenderness over the anterior and posterior joint line may be present. Greater trochanter is usually thickened and elevated. Prominence of greater trochanter is due to lateral subluxation, muscle wasting, coxa vara and relative overgrowth of greater trochanter. Limitation of range of movements especially abduction and internal rotation seen. Fixed flexion deformity is seen. In the normal hip, rotations are more in 90 degree flexion than extension, called differential limitation of rotations. In LCPD, rotations are more limited in flexion than extension. Those children on skin traction may show near normal range of movements.

In adolescence, the hip is in healed stage and the physical findings depends on the amount of incongruity, impingement and femoral neck shortening. Residual deformity can cause intra-articular and extra-articular impingement. Many patients present with pain due to impingement. Shortening of variable degree is present. Adults present with pain and limitation of movement due to early onset osteoarthritis. Limitation of movements affects abduction and internal rotation, but other movements are affected as per severity of degenerative changes. External rotation deformity is seen in those with advanced degenerative changes. Flexion deformity and adduction deformity also is seen in those with severe incongruity or osteoarthritic changes.

Imaging

Diagnosis is usually made with the conventional x-rays, but radiological changes usually appears late. Hence recent trend is to rely on advanced imaging modalities such as perfusion MRI using gadolinium.

A correctly positioned AP view, false profile view of acetabulum and frog leg lateral view (Lowenstein view) should be taken in all patients suspected to have LCPD. AP view is taken in 15 degrees of internal rotation with the beam centred over a point midway between the superior margin of pubic symphysis and a line connecting both ASIS. If properly positioned the ilium, tear drop, obturator foramen should be symmetrical, the tip of coccyx should be in the midline in line with pubic symphysis and the distance from tip of coccyx to symphysis pubis should be within 2cm. 

The AP radiograph is used to measure the following radiographic parameters: lateral center edge angle, acetabular index, Shenton’s line and femoral head extrusion index. Look for the head at risk signs. Initial x-rays may be normal. Radiographic changes appear about 6 months after the first infarction has occurred. Earliest radiologic sign is a relatively smaller size of ossific nucleus of the involved head of femur.

Widening of medial joint space is found early seen (Waldenström sign). Widening of joint space due relative smaller size of ossific nucleus, lateral subluxation and thickening of articular cartilage.

Later the ossific nucleus becomes progressively sclerotic. Subchondral fracture may be seen. Subchondral fracture is called Caffey’s sign. Fragmentation and collapse leads to progressive deformation of femoral head. Lateral extrusion of head occurs with flattening of epiphysis. Shenton’s line shows superolateral migration of femoral head. Shenton’s line is considered to be broken if there is a step off of more than 5mm. Although changes are more noticeable in the proximal femur, acetabular changes are frequently present. Osteoporosis of acetabular roof, alterations in contour and change in dimensions is often seen. Acetabulum may show bicompartmentalization, ischium varum and early closure of triradiate cartilage. Acetabulum becomes shallow and misshapen. 

False profile view is taken with the patient standing and the body tilted 65 degrees to the x-ray beam, with the uninvolved side forward. On the false profile view of acetabulum measure the vertical centre edge angle. 

Catterall has described several radiographic findings as head-at-risk signs as indicators of poor prognosis. These are lateral extrusion, calcification lateral to the epiphysis, poorly ossified lateral part of epiphysis (Gage sign- Described by Courtney Gage in 1933), diffuse metaphyseal reaction (described by Smith in 1982) and horizontal growth plate. 

Measure the Heyman Herdon acetabular head index, Dickens and Menelaus femoral head extrusion index and Reimer migration index.

If containment surgery is planned, x-rays are repeated in hip abduction and in abduction-internal rotation to assess containment. Arthrography through an anterolateral or subadductorl access is an important adjunct to preoperative assessment as it visualizes the contour of articular cartilage and allows dynamic assessment of hip joint congruity. On the arthrogram assess the presence or absence of impingement, amount of subluxation manifested by medial clear space, presence or absence of hinged abduction and containment of femoral head within the confinements of acetabulum.

Bone scan findings precedes radiographic signs by 3 months. It is rarely used due to risk of radiation. CT is almost never used in children, but can be of use in adults to study impingement or to assess adequacy of columns before total hip replacement. 

Conventional radiography and x-ray based classifications have the limitation of inability to visualize the shape and deformation of cartilage. In addition, radiographic changes are present only in later stages of the evolution of LCPD. MRI has the advantage of visualization of cartilage and allows early detection of osteonecrosis. It is useful in detection of full extent and exact location of osteonecrosis, visualization of physis, chondral pathology and labral lesions. Epiphyseal changes are not associated with growth arrest in 76% of cases, but physeal and metaphyseal changes are associated with growth arrest.

MRI avoids ionizing radiation and is noninvasive. However, unenhanced MRI may fail to show changes in early stages of disease. Perfusion of the head can be studied using dynamic gadolinium enhanced subtraction MRI. MR perfusion index has been described as a measure of epiphyseal perfusion using digital image analysis of gadolinium enhanced subtraction MR images. It has been shown to correlate with femoral head deformity measured using conventional follow up x-rays. Necrosis extension, lateral extrusion, and the extent of physeal and metaphyseal involvement on MRI are important predictors of outcome. Horizontalization of labrum can also be identified on MRI which is indicative of significant femoral head deformation. Metaphyseal changes have been shown to be important predictors of physeal involvement and prognosis.

Classification

Classification can describe the extent and severity of disease at the time of presentation or its outcome. Classification help in predicting prognosis, deciding on treatment, comparison of treatment.

Waldenström Staging (1938)

Necrosis stage– Small sclerotic head with increased medial joint space.

Fragmentation stage– Epiphysis sclerotic, fragmented and collapsed.

Re-ossification stage– Reossification proceeding from lateral to medial and posterior to anterior

Healed stage– Density returned to normal with residual changes in shape and size of head.

Elizabethtown Classification

4 stages 

  1. Sclerotic 
    1. Without loss of height
    1. With loss of height
  4. Fragmentation
    1. Early
    1. Late
  7. Healing
    1. Peripheral – <1/3rd>1/3rd
  9. Healed

Catterall Classification (1971)

Group 1– <25% involvement. Anterior epiphysis only involved. No collapse, no metaphyseal involvement. Usually revascularised.

Group 2– Up to 50% involved. Collapse present. Central segment fragmentation and collapse. Necrotic portion appears sclerotic. Epiphyseal height maintained. Necrotic portion separated from viable portion on the lateral view in a characteristic ‘V’.

Group 3– >50% but not total involvement. Anterior, central and lateral involvement. Posterior part of head remains viable. Head-within-head appearance. Collapse present. Extensive metaphyseal changes with broadening of neck.

Group 4– Whole epiphysis affected. Collapse present. Mushroom shaped head. Extensive metaphyseal changes.

Described 4 “head-at-risk signs”

         1, Lateral subluxation

         2, Calcification lateral to the epiphysis

         3, Gage sign- Inverted V shaped defect laterally)

         4, Horizontal growth plate

         5, Diffuse metaphyseal reaction described by Smith in 1982

Salter Thomson Classification (1984)

It can be applied only in presence of subchondral fracture. Extent of subchondral fracture correlates with extent of subsequent collapse.

Group A– Subchondral fracture extent <50% of epiphysis.

Group B– Extent of subchondral fracture >50% of head.

Herring Lateral Pillar Classification (1992)

Done in the fragmentation stage. Epiphysis divided into lateral, central and medial pillars on the true AP view. Lateral pillar is the lateral 5-30% of epiphysis depending on the location of lucent line that separates it from the central necrotic area. If lucent line is absent, take the lateral 25% as lateral pillar. Maximum reduction in the height of lateral pillar measured in relation to normal side.  It is difficult to apply in bilateral cases and in the very young.

Group A– lateral pillar height fully maintained

Group B– Lateral pillar height >50% of normal. Good outcome if age is <9 years.

Group B/C– Lateral pillar height 50%, but poorly ossified. Added in 2004.

                            B/C1– Only 2-3mm width

                            B/C2– Minimum ossification

                            B/C3– Lateral pillar more depressed that central pillar

Group C– Lateral pillar height <50% of normal

All group A have good result. 2/3 of group B have good results. Only 25% of group B/C have good result. Only 1 in 8 with group C have a good result. 

Difficult to classify very young children. Needs about 7 months for proper classification. About 30% needs upgrading and only 4% remain in group A on subsequent follow up. Difficult to classify in bilateral cases.

Mose Classification

Done to assess outcome. Done on x-rays taken after 16 years of age. Classified into 3 types by placing Mose template with concentric circles at 2mm increments. Assess the sphericity of head.

Spherical

Nonspherical

Spherical but crescent shaped

Fasting scintigraphy classification(1980)

Grade 1– Decreased activity in <25% of head

Grade 2– Decreased activity in 50% of head

Grade 3– Decreased activity in 75% of head

Group 4– Decreased activity in whole of head

Conway Scintigraphy Classification (1992)

2 tracks. Track A of recanalization and Track B of neovascularization.

4 stages in each track.

Track A- 

         Whole head

         Lateral column

         Anterior and medial extension

         Complete

Track B

         Whole head

         Base filling

         Mushrooming

         Complete

Stulberg Classification 1982

Head shape divided into spherical (I or II), ovoid (III) or flat (IV or V). Subdivided according to coxa magna, steep acetabulum, short neck, 

I-      Normal

II-      Spherical – Within the circle by <2mm in both AP and lateral views. Coxa magna, short neck, acetabulum steep.

III-    Ovoid head. Out of shape by >2mm on either AP or lateral views

IV-    Aspherical congruency– Aspherical. Congruent.

V-      Aspherical incongruency– >1cm flattening on the superolateral weight bearing area. Incongruent.

I and II are spherical congruency, III and IV are aspherical congruency and V is aspherical incongruency.

Laredo Arthrographic Classification

Nature and extent of femoral head deformation and the severity of lateral extrusion are the most important factors that determine the prognosis. Radiographs show only the ossific portion proximal femoral epiphysis and may not represent the anatomical reality of the femoral head acetabular congruence. The understanding of the status of the cartilaginous portion is important especially in presence of persistent restriction of motion. However, it is an invasive procedure and difficult to repeat. Horizontalization of labrum is an important finding suggestive of deformation of head and it can be quantified by measuring the labral angle.

Group I – Normal hip

Group II

Femoral head larger than normal but spherical

Extrusion present at the neutral position and absent at 30 degrees’ abduction and slight internal rotation.

Group III

Femoral head larger than normal and ovoid

Extrusion present at neutral position and in 30 degree abduction and slight internal rotation.

Group IV 

Femoral head larger than normal and flattened

Extrusion is present at 30 degrees’ abduction and slight internal rotation 

Labrum loses its concavity and becomes elevated and straightened Hinged abduction present.

Group V

Femoral head larger than normal and saddle shaped

Extrusion is present at neutral position and in 30 degrees’ abduction and slight internal rotation.

Labrum is elevated and sometimes everted, with abnormal pooling of contrast medium at the saddle deformity area. 

Sphericity Deviation Score

Mark the medial and lateral edge of primal femoral growth plate on the AP and lateral views. Draw the maximum inscribed circle (MIC) touching these points without extending outside the femoral head. Mark the centre of the circle. Draw a second concentric circle as the minimum circumscribed circle (MCC) without extending inside the femoral head. Measure the difference between the radii of MIC and MCC (roundness error) on both AP and lateral views. Measure the difference between radii of femoral head on the AP and lateral views (ellipsoid deformation). The sum of roundness error on the AP and lateral views and the ellipsoid deformation is the Sphericity Deviation Score. SDS of normal hip is 0-3.8. If SDS at healing is less than 10, then the chance of hip having Stulberg I or II is high. If SDS is more than 20, then the hip is likely to have higher Stulberg grades at maturity.

Prognosis

60-80% of patients with LCPD have good outcome but it deteriorates on long term follow up. At a mean age of 45 years, 86% percentage of hips were found to be functioning and only 8% were found to have arthroplasty. But another report published later on the same group of patients at an average age of 53 years found that 40% of hips were replaced, 40% had functioning hips and 20% had osteoarthritic symptoms.  

Long term sequelae of LCPD are due to nonspherical head, short and broad neck, greater trochanteric overgrowth and labro-acetabular changes. Severity of these changes depends on the age of onset, gender, extent of femoral head necrosis, severity of femoral head deformation and method of treatment.

Age at onset between 5-7 years do better than those with age at onset more than 8-9 years. Catterall group III and IV patients with age at onset younger than 6 years may have poor outcome. In the multicenter study by Legg Perthes study group 59% of those aged less than 8 years at onset had a Stulberg II outcome while only 39% of those aged more than 8 years had a Stulberg II outcome. According to a study by Wiig from Norway 59% of those aged less than 6 years had a Stulberg I or II outcome and 38% of those above 6 years had a similar outcome.  

Age at the time of healing considered to be more important than age at onset. Age at follow up is also important with 86% having osteoarthritis at 65 years of age. About 50% of patients will ultimately need a total hip arthroplasty.

Lateral pillar classification also is helpful in prognosis determination. Stulberg I to II outcome found in 70-100% of lateral pillar A hips, 51-62% of lateral pillar B hips, 28% in B/C borderline hips and 13-30% of C hips.

Caterall grading also is significant in prognosis. 84% of Catterall 1 and 2 have a Stulberg I or II outcome and only 44% of Catterall 3 or 4 have a Stulberg I or II outcome.

Girls have poor outcome when compared to boys of same age due to more advanced skeletal age. Outcome is poor especially in girls aged more than 8 years. Overweight, longer duration for healing, persistent restriction of motion found to be associated with poor outcome.

Radiologically the following are important; extent of epiphyseal involvement, extent of metaphyseal changes, extent of lateral extrusion >20% and height of lateral pillar <50%. 

Method of treatment has a bearing on outcome in those aged more than 8 years with lateral pillar B or B/C with 73% of lateral pillar B treated by surgery having Stulberg I or II outcome while only 44% of those treated nonoperatively have a similar outcome. Greater trochanteric overgrowth is more common in lateral pillar C (44%) than in type B and B/C groups.41

 3 points from the Perthes Study Group regarding prognosis

1, Children with onset at less than 8 years are likely to have better outcomes. Generally lower age at onset have a better prognosis, but only half of those with age less than 5 years at onset with lateral pillar C have a good outcome.

2, Children more than 8 years at onset, if at least 50% of lateral pillar height maintained have better results if treated by surgery.

3, Outcome in Type C hips with less than 50% lateral pillar height is generally poor irrespective of treatment method.

Treatment

”TO BE CONTINUED”

Topics

Brachial Plexus Injuries in Adults

Introduction

The brachial plexus prone for injury because of following reasons.

  • The upper limb is connected to the axial skeleton mainly by the soft tissues, with the only bone connection of upper limb to axial skeleton being the clavicle.
  • Supraclavicular portion of brachial plexus is relatively superficial.
  • The shoulder girdle has a wide arc of movement.

These factors increases the risk  injury especially to the brachial plexus.

History

Homer described brachial plexus injury in the duel between Hector and Teucrus in Iliad.

1947- Seddon described nerve grafting.

1961- Yeoman and Seddon described intercostal nerve transfer.

1966- SICOT congress in Paris reached a consensus to discourage surgery for BPI due to discouraging results.

1970s- Work by Millesi in Vienna and Narakas in Lausanne demonstrated the utility of brachial plexus reconstruction

Anatomy

  • Dorsal roots (sensory) and ventral roots (motor) unite to form the spinal nerve.
  • The spinal nerve divides into dorsal and ventral rami. Dorsal rami supply the muscles and skin of paravertebral region.
  • The ventral rami of C5-C8 and T1 merge and decussate to form the brachial plexus with variable contribution from C4 and T2 between the anterior and middle scalene muscles. The brachial plexus can be divided to roots, trunks, divisions, cords and individual nerves.
  • Trunks are formed in the interscalene triangle. Cords are formed distal to the outer margin of first rib. Cords are named according to their relationship to the second part of axillary artery situated posterior to the pectorals minor.
  • C5 and C6 ventral rami unite to form the upper trunk (C5-6). C7 continues as middle trunk  (C7). C8 and T1 unite to form the lower trunk (C8-T1).
  • Each trunk divides into anterior and posterior divisions. The anterior divisions of upper and middle trunk unite to form the lateral cord (C5,6,7). The anterior division of lower trunk continue as medial cord (C8-T1). Posterior divisions of upper, middle and lower trunks unite to form the posterior cord.
  • Individual nerves may arise from the roots, trunks or cords of brachial plexus.
  • No nerves arise from the divisions of brachial plexus.
  • The phrenic nerve, long thoracic nerve and dorsal scapular nerve arises from the roots.
  • Long thoracic nerve arises from C5, C6 and C7 roots and supplies the serratus anterior.
  • Dorsal scapular nerve arises from C5 root and supplies the levator scapulae and the rhomboids major and minor.
  • The nerve to subclavius (C5) and suprascapular nerve (C5,6) arise from the upper trunk.
  • Suprascapular nerve (C5,6) supplies the supraspinatus, infraspinatus and teres minor.
  • Lateral cord (C5,6,7) gives rise to lateral pectoral nerve, musculocutaneous nerve  and lateral root of medial nerve (Mnemonic- LML).
  • Medial cord (C8,T1) gives rise to medial cutaneous nerve of arm, medial cutaneous nerve of forearm, medial root of median nerve, medial pectoral nerve and ulnar nerve (Mnemonic- MMUMM).
  • Posterior cord gives rise to subscapular nerve, thoracodorsal nerve, axillary nerve  and radial nerve (Mnemonic- STAR).

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Topics

Plantar Plate Insufficiency or Rupture (Turf Toe)

Anatomy

  • During normal gait, MTPJ has to sustain more than 40 to 60% off bodyweight, during normal athletic activities this increases to 2-3 times the bodyweight. During running jump MTPJ sustains eight times the body weight.
  • Metatarsophalangeal joint (MTPJ) is statically stabilised by the plantar plate and the collateral ligaments.
  • Dynamic stability for the first MTPJ is provided by the short flexor complex, which is composed of medial and lateral bellies of flexor hallucis brevis, adductor hallucis and abductor hallucis muscles and the medial and lateral sesamoid bones and their ligaments.
  • Plantar plate is the trapezoid shaped thickening of the MTPJ capsule at the weight bearing plantar aspect.
  • It is a fibrocartilaginous structure that resists hyperextension and provides stability to the MTPJ.
  • It is the major stabiliser of the MTPJ.
  • It provides a smooth gliding surface for the flexor tendons inferiorly and metatarsal head superiorly.
  • Proximally it is inserted into the metatarsal neck.
  • Distally to the base of proximal phalanx by medial and lateral longitudinal bundles.
  • It receives attachment from collateral ligaments, deep transverse metatarsal ligaments and vertical fibers of plantar aponeurosis.

Pathology

  • Degenerative or traumatic rupture of plantar plate is an under-recognised cause of metatarsalgia.
  • Degenerative rupture of plantar plate especially in the second MTPJ can lead to metatarsalgia with synovitis, which if untreated progresses to hammer-toe, claw-toe or crossover-toe deformity.
  • In 2/3rd of cases the second toe is commonly involved as it tis the longest.
  • Long term use of high heel foot wear may be a cause in older women as it causes chronic
  • Lesions can cause metatarsalgia, instability, deformity and dislocation.
  • Deformity may be in the sagittal plane such as hammertoe and claw toe or coronal plane such as crossover toe..
  • During the heel-off and toe-off of stance phase of gait, the MTPJ becomes dorsiflexed. Dorsiflexion is passively resisted by the plantar plate and actively by the intrinsic musculature.
  • With insufficiency of plantar plate, dorsal subluxation of MTPJ occurs. The interossei is displaced dorsally leading to hyperextension of MTPJ. The medially located lumbrical causes adduction deformity. Attenuation of collateral ligaments also contributed to the development of coronal plane deformity.
  • Majority of cases have an insidious onset and is seen in sedentary older women.
  • It can be seen in young athletic males after trauma.
  • It can also be seen as a secondary deformity in association with hallux valgus, hallux varus, pes planus and hallux rigidus.
  • The term Turf Toe introduced by Bowers and Martin in 1976 for injuries of the plantar plate of first metatarsophalangeal joint (MTPJ) of great toe seen in athletes playing on artificial turfs using lighter and flexible shoes.
  • Coughlin coined the term ‘second crossover toe’ in 1987 to describe the coronal plane deformity.
  • Hyper-dorsiflexion of the MTPJ is the most common mechanism of injury.
  • Causes distractive forces on the plantar plate, sesamoid complex and toe flexors.
  • In the big toe, the plantar plate rupture occurs distal to the sesamoids.
  • Rarely tissue disruption occurs through the sesamoids producing sesamoid fracture.
  • Injury may be partial or complete. It may extend to the collateral ligaments in presence of varus or valgus moment.
  • Hyper-plantarflexion injury is called Sand Toe as it is common in beach volleyball.

To read the complete article

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Topics

Femoroacetabular impingement

Definition Early pathological contact between bony prominences of femur and acetabulum during hip motion due to a variety of morphological conditions leading to pain and chondrolabral damage predisposing the patient to early osteoarthritis of hip.

Introduction

• First described in 2003 by Prof Reinhold Ganz from Bern Hip Group, Switzerland.

• Impingement may be intra-articular or extra-articular.

• Intra-articular impingement may be of 3 types

○ Cam

○ Pincer

○ Combined-86%

• Abnormal morphology and / or motion is required for clinically relevant impingement to occur.

• In addition a subluxating impingement also has been described by Leunig in 2001 in patients with shallow and dysplastic acetabulum.

Cam type impingement

• Loss of normal head neck offset is the underlying cause.

• The hump at the femoral head neck junction and the loss of normal concavity of the superior border of neck of femur is called pistol grip deformity.

• Anterior hump causes outside-in abrasion of labrum and cartilage in the anterosuperior part of acetabulum on flexion and internal rotation.

• Mismatch between femoral head and acetabulum leads to abutment of aspherical head and acetabulum rim leading to shear stresses which causes injury to the labrum and cartilage.

• Chondrolabral separation, cartilage delamination and chondral defects develop leading to osteoarthritis.

Pincer type impingement

• Acetabular overcoverage is the underlying cause.

• Overcoverage may be localized or generalized.

• Overcoverage may be due to increased acetabular depth, abnormal version of acetabulum or localized bone overgrowth.

• Leads to labral damage, ossification of labrum and cartilage damage over a circumferential narrow strip at the rim of acetabulum.

• Impingement may lead to subluxation of head in the opposite direction leading to contre-coup cartilage lesions.

Clinical assessment

• Young in their 20-40s.

• Presents with groin pain in the sitting position.

• Pain during or after sports activities

• Internal rotation and flexion are typically limited.

• Anterior impingement test- Groin pin on forced internal rotation and adduction in 90 degrees of  flexion.

• Posterior impingement test- Pain on hyperextension and external rotation of hip.

• Drehmann’s sign- Unavoidable passive external rotation on flexion (axis deviation) due to anterior impingement.

Imaging

• Anteroposterior and lateral views of the pelvis with both hips are taken.

• Identify the abnormal morphology of acetabulum and femur.

• Identify labral and cartilage damage.

• Herniation pits or Pit’s pits are seen in FAI.

• In cam impingement, the characteristic chondrolabral damage is seen in the anterosuperior part of acetabulum.

• In pincer impingement chondrolabral damage is seen posteroinferiorly.

• Quantify the degree of osteoarthritic changes

○ As positioning for x-rays can alter the measurements first ensure proper positioning of x-rays.

○ Acetabular coverage- CE angle, Acetabular index, Extrusion index

○ Acetabular depth- Kohlers line

○ Acetabular version

   § Posterior wall sign- Posterior margin of acetabulum lies medial to the centre of femoral head.

   § Cross over sign- Posterior margin of acetabulum crosses the anterior margin and the inferior part of posterior margin lies medial to the anterior margin.

   § Ischial spine sign- Prominent ischial spine projecting medial to the pelvic brim is a sign of retroversion of acetabulum

  ○ Femoral head neck asphericity.

   § Alpha angle- Described by Notzli. <50 degrees. >55 degrees indicates loss of femoral head neck offset. Measured ideally on the radial slices taken along the axis of femoral neck. Angle between the axis of femoral head and neck and the line drawn between center of femoral head and the head neck junction.

   § Head neck offset less than 10mm.

  ○ Femoral neck shaft angle

• Varus and valgus deformity of proximal femur may also may contribute to the development of impingement.

• Torsional deformity especially of the acetabulum is an important cause of impingement.

• Conventional MRI with orthogonal slices cannot fully visualize the labral and chondral lesions of FAI.

• MR Arthrography with radial slices is the gold standard for assessment of FAI.

• Delayed Gadolinium-enhanced MRI of cartilage (dGEMRIC) allows quantitative assessment of chondrolabral damage.

Treatment

• Depends on the age and activity profile of the patient.

• Asymptomatic individuals generally doesn’t need treatment.

• If significant osteoarthritic changes are present then total hip replacement is the treatment of choice.

• In the absence of OA changes; treatment depends on the type of impingement, location of impingement and degree of acetabular and femoral version.

• Aim of treatment in cam impingement is restoration of sphericity of the femoral head by reshaping the head neck junction.

• Cam impingement is treated by osteochondroplasty.

• Isolated anterosuperior cam impingement can be treated by arthroscopy.

• Cam impingement close to the site of entry of epiphyseal vessels, posterior cam and multiple pathologies need open treatment by safe surgical dislocation.

• Safe surgical hip dislocation is the gold standard in the treatment of FAI.

• Lateral approach through the Gibson interval between gluteus medius and gluteus maximus utilized.

• Z- capsulotomy with preservation of labrum, short external rotators, pyriformis and the medial circumflex artery.

• Anterior limb of capsulotomy is close to the femoral attachment of capsule and the superior limb is at the acetabular attachment of capsule.

• Aim of treatment in pincer impingement is to reduce acetabular overcoverage.

• Pincer impingement needs careful assessment of acetabular version.

• Severe retroversion of acetabulum needs periacetabular osteotomy to restore normal anteversion of acetabulum.

• If acetabular version is normal then pincer impingement is treated by rim trimming and labral reattachment.