Updated: 7/8/2021

Adult Limb Deformity

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  • Summary
    • Adult Limb Deformity is a lower extremity condition that can result from childhood growth impairment, metabolic bone disorders, severe osteoarthritis, trauma, or fracture malunion/nonunion.
    • Diagnosis is made with a combination of clinical examination and plain full limb length radiographs.
    • Treatment is usually osteotomy of the femur and/or tibia, although arthroplasty may also correct deformity in appropriate patients.
  • Epidemiology
    • Incidence
      • varies depending on the underlying cause of the deformity
    • Demographics
      • no gender predilection
      • age
        • younger patients
          • more likely due to trauma/childhood growth abnormalities
    • Location
      • upper extremity - rare
        • deformity is commonly seen at elbow and wrist secondary to fracture malreduction
      • lower extremity (focus of this topic)
        • femur vs. tibia or both
          • location of deformity helps determine where correction should be made
        • proximal vs. distal
    • Risk factors
      • family history
      • trauma
  • Etiology
    • Pathophysiology
      • mechanism of injury
        • related to associated injury or orthopedic condition that contributes to bony limb deformity
      • pathoanatomy
        • in most cases, the anatomic axis of bone is altered for some reason (malunion/nonunion, metabolic bone disease, etc) to the point where there is significant mechanical axis deviation (MAD), leading to altered joint contact pressures and ligamentous stability, which further contributes to joint degeneration and worsening of mechanical alignment over time
    • Associated conditions
      • orthopaedic conditions
        • malunion
        • nonunion
        • previous osteotomies
        • genu valgum/genu varum
        • advanced arthritis with deformity
        • childhood abnormalities
          • blount's disease
          • focal fibrocartilaginous dysplasia
          • proximal tibial physeal injury
          • cozen's phenomenon
          • skeletal dysplasia
            • spondyloepiphyseal dysplasia (SED)
            • metaphyseal dysplasia (MED)
        • femoral anteversion
        • limb length discrepancy (LLD)
        • bony tumors
      • medical conditions
        • metabolic bone disorders
          • renal osteodystrophy
          • rickets
            • vitamin D deficient
            • hypophosphatemic rickets
          • osteogenesis imperfecta
        • neuromuscular disorders
          • cerebral palsy
        • neurofibromatosis
  • Anatomy
    • Osteology
      • femur
        • normal proximal femur neck shaft-angle 130 +/- 7º
        • normal proximal femur anteversion 10 +/- 7º
        • tip of greater trochanter should be at the level of the center of femoral head and is used as the start point for measuring the anatomic axis of the femur (AAF)
        • difference between anatomic and mechanical femoral axes is normally 5-7º
      • tibia
        • shaft is triangular in cross-section
        • tibial tubercle sits anterolaterally and attaches to patellar tendon
        • anatomic and mechanical tibial axes should be equal if no deformity exists
    • Ligaments
      • knee
        • medial collateral ligament (MCL) - superficial MCL (sMCL) and deep MCL (dMCL)
          • sMCL attaches just posterior to medial epicondyle on femur and 6 cm distal to joint line on tibia
          • dMCL attaches has meniscofemoral and meniscotibial attachment sites
        • lateral collateral ligament (LCL)
          • attaches posterior to lateral epicondyle on femur and anteriorly on fibular head
        • both LCL and MCL contribute to coronal plate stability and can complicate deformity
          • abnormal joint line congruence angle JLCA (>2º) is indicative of soft tissue laxity around the joint
  • Classification
    • Descriptive based on bone(s) affected, position (varus/valgus, procurvatum/recurvatum, etc.) and degree of deformity
    • Nature of deformity
      • angulation, translation, length, and rotation should be evaluated
        • should be corrected in that order
  • Presentation
    • History
      • prior trauma or childhood deformity/bone disease with/without progression
    • Symptoms
      • common symptoms
        • pain with location based on deformity
          • varus deformity = medial knee pain
          • valgus deformity = lateral knee pain
        • subtle to obvious deformity
        • complaints of abnormal gait or loss of function
    • Physical exam
      • inspection
        • note coronal/sagittal plane deformity
        • note any rotational deformity
          • femoral anteversion - increased IR >70º
          • residual increased external tibial torsion
        • limb-length discrepancy
      • motion
        • range of motion (ROM) at the hip, knee and ankle should be evaluated
        • ligamentous laxity should be evaluated
  • Imaging
    • Radiographs
      • recommended views
        • weight-bearing AP & lateral full-length lower extremity views
          • patellas should be facing directly anterior for correct rotational profile
          • x-ray tube should be placed 10 ft away from cassette at the level of the knees
        • weight-bearing AP & lateral views of each affected limb segment
      • findings
        • anatomic axis - measured on each anatomic segment
          • femur (AAF)
            • bisects medullary canal of femur
            • measured from tip of greater trochanter distally to knee
            • typically exits just medial to midpoint of distal femur
          • tibia (AAT)
            • bisects medullary canal of tibia
            • measured from center of proximal tibia to distal tibia
        • mechanical axis
          • limb
            • line from center of femoral head to center of ankle
          • femur (MAF)
            • line from center of femoral head to center of distal femur
          • tibia (MAT)
            • line from center of proximal tibia to center of ankle
            • should be same as AAT if there are no deformities of tibia
        • joint line axes
          • femur
            • line connecting the distal aspects of the medial/lateral femoral condyles
          • tibia
            • line connecting the proximal aspects of the medial/lateral tibial plateau
      • measurements
        • coronal plane
          • anatomic/mechanical angle
            • relationship between anatomic and mechanical angles
              • femur: 5-7º
              • tibia: AAT = MAT in most cases
          • mechanical axis deviation (MAD)
            • occurs when mechanical limb axis does not pass through center of knee
              • MAD lateral to center of knee = valgus alignment
              • MAD medial to center of knee = varus alignment
          • anatomic axis measurements - denoted with lowercase 'a'
            • femur
              • medial proximal femoral angle (aMPFA) - normal: 84º (80-89º)
              • lateral distal femoral angle (aLDFA) - normal: 81º (79-83º)
            • tibia
              • medial proximal tibial angle (MPTA) - normal: 87º (85-90º)
              • lateral distal tibial angle (aLDTA) - normal: 89º (86-92º)
          • mechanical axis measurements - denoted with lowercase 'm'
            • femur
              • lateral proximal femoral angle (mLPFA) - normal: 90º (85-90º)
              • lateral distal femoral angle (mLPFA) - normal: 87º (85-90º)
            • tibia
              • medial proximal tibial angle (MPTA) - normal: 87º (85-90º)
              • lateral distal tibial angle (mLDTA) - normal: 89º (86-92º)
          • joint line convergence angle (JLCA)
            • JLCA of femur and tibia should be essentially parallel
              • normal = within 0-2º of each other
        • sagittal plane measurements
          • posterior distal femoral angle (PDFA) - normal range: 79-83º
          • posterior proximal tibial angle (PPTA) - normal range: 77-84º
        • leg length discrepancy (LLD)
          • difference between distance from top of femoral head to center of ankle joint on each limb
          • can measure femur and tibia separately to determine source of structural LLD
        • deformity calculation
          • center of rotation and angulation (CORA) is the intersection of proximal and distal mechanical axes of a deformed bone when the deformity is solely angular
          • if the deformity is a combination of angulation and translation, the CORA will move from the site of mechanical axis intersection
      • criteria dictating treatment
        • abnormal values help determine the site of deformity and site/degree of correction needed
          • coronal vs. sagittal plane
          • femur vs. tibia or both
          • proximal vs. distal
            • deformity closer to joint will have greater effect on angulation at that joint
    • CT
      • indications
        • rotational malalignment
      • views
        • axial, sagittal, coronal sequences
      • findings
        • axial cuts particularly helpful for establishing femoral version and axial malalignment
  • Treatment
    • Nonoperative
      • bracing/orthoses
        • indications
          • subtle deformity within limits of radiographic parameters listed above
          • deformity with minimal functional deficit
          • unable to undergo surgical intervention
      • modalities
        • dependent on etiology of deformity
          • bracing
          • orthoses (knee-ankle foot)
      • outcomes
        • bracing is often not well tolerated
        • minimal data exists to demonstrate risk of deformity progression with nonoperative management
    • Operative
      • osteotomy
        • derotational femoral osteotomy
          • indications
            • no absolute indications
            • relative indications
              • excessive femoral anteversion, < 10º of external rotation
                • patellar maltracking and instability caused by increased femoral internal rotation
              • gait disturbance with difficulty running
          • techniques
            • proximal intertrochanteric vs diaphyseal vs. distal supracondylar location
            • blade plate vs. locking plate vs. intramedulllary nail for fixation
          • outcomes
            • all forms of derotational osteotomies appear to show improved outcomes
            • ideal degree of version correction remains debated
            • may have undesired impact on coronal plane alignment
        • valgus-producing tibial osteotomy
          • indications
            • varus MAD with MPTA < 85º and CORA located within tibia, indicating that tibia is cause of varus malalignment
            • no clinical or radiographic evidence of arthritis in other two compartments
            • usually performed in younger patients that are not good candidates for total knee arthroplasty (TKA) or who have larger tibial deformity not amenable to treatment with primary TKA
          • techniques
            • medial opening wedge tibial osteotomy
            • lateral closing wedge tibial osteotomy
          • outcomes
            • significant improvements in MAD and outcome scores (Lysholm, SF-36,VAS)
              • 90-95% excellent results at 5 years, decreased to 50-70% at 10 years
            • higher failure rates in smokers, age>60, and concomitant arthritis in other two compartments
        • valgus-producing femoral osteotomy
          • indications
            • varus MAD with increased mLDFA (>90º) or aLDFA (>83º) and CORA located within the femur, indicating femoral contribution to varus malalignment
            • joint line obliquity after valgus-producing tibial osteotomy if deformity in both tibia and femur
          • techniques
            • lateral closing wedge osteotomy
          • outcomes
            • improvements in MAD and outcome scores
        • varus-producing femoral osteotomy
          • indications
            • valgus MAD with decreased mLDFA (<85º) or aLDFA (<79º)
              • valgus deformity >12º
              • clinical and radiographic evidence of no medial compartment arthritis
            • relative indications
              • may help improve patellar tracking in cases of genu valgum with increased Q angle
              • may be useful in cases of MCL stress due to valgus alignment
          • techniques
            • lateral distal femoral opening wedge osteotomy
          • outcomes
            • safe, reproducible and effective at normalizing valgus malalignment
      • gradual limb lengthening (LLD)
        • indications
          • >2 cm LLD compared to contralateral side, although specific degree of LLD is not absolute indication/contraindication
        • techniques
          • external fixator
          • intramedullary device +/- external fixator
        • outcomes
          • significantly improved LLD to <1 cm deficit
          • also has the ability to concomitantly correct a small degree of angular deformity, particularly in diaphyseal or metaphyseal location
      • total knee arthroplasty (TKA)
        • indications
          • deformity about the knee joint in setting of multi-compartmental arthritic changes
        • techniques
          • primary TKA with normal implants
          • primary TKA with stemmed implants
            • consider in cases with ligamentous laxity or after osteotomy that compromises collateral integrity
          • TKA after extra-articular osteotomy
        • outcomes
          • consistent improvement in outcome scores
          • able to correct coronal alignment to within several degrees of neutral
            • easier with CORA further from joint
          • more complicated and results less reliable after extra-articular osteotomy
  • Techniques
    • Bracing/orthoses (KAFO)
      • technique
        • consists of an AFO with metal uprights, a mechanical knee joint and two thigh bands
    • Derotational femoral osteotomy
      • approach
        • lateral approach to femur or medial femur subvastus approach depending on technique used
      • technique
        • proximal osteotomy
          • intertrochanteric or subtrochanteric osteotomy performed
          • fixed with blade plate or locking plate
          • also able to correct flexion/extension and varus/valgus deformity
        • diaphyseal osteotomy w/ intramedullary fixation
          • small stab incision laterally over femoral isthmus
          • drill holes used to begin osteotomy
          • intramedullary nail inserted proximally at greater trochanter
          • once nail is passed to level of fracture site, osteotomy can be completed
          • femur is then derotated to 45º of external rotation and 45º of internal rotation with patella in line/slightly externally rotated relative to the ASIS
        • distal supracondylar osteotomy
          • medial subvastus approach
          • schanz pins inserted in proximal and distal segments followed by osteotomy
          • once segment derotated, supracondylar locking plate placed
      • complications
        • under correction
        • over correction causing retroversion and out-toeing
          • rare
    • Valgus producing tibial osteotomy
      • approach
        • lateral closing wedge osteotomy
          • anterolateral
        • medial opening wedge osteotomy
          • anteromedial
      • technique
        • lateral closing wedge osteotomy
          • resect anterior aspect of fibular head
          • osteotomy performed proximal to tuberosity under fluoroscopy
          • wedge removed laterally, with intact medial cortex acting as hinge
          • fixation with staples or plate
        • medial opening wedge osteotomy
          • biplanar alignment guide used
          • place hinge pin from medial to lateral, exiting just below lateral tibial plateau
          • cutting guide placed, patellar tendon protected
          • osteotomy created and packed with bone wedge
      • complications
        • nonunion
        • patellar tendon injury
        • patella baja
        • alterations in tibial slope
          • increases after opening wedge more likely
          • decreases after closing wedge more likely
    • Valgus producing femoral osteotomy
      • approach
        • lateral subvastus approach to distal femur
      • technique
        • lateral closing wedge femoral osteotomy
          • k-wires inserted from laterally at supracondylar femur directed distally aimed at the far medial cortex just proximal to the medial femoral condyle
          • hinge through medial cortex without perforating
            • intact medial cortex provides higher axial/rotational stability after osteotomy
          • closure of wedge with gentle valgus force
          • biplanar vs. uniplanar osteotomy
      • complications
        • nonunion
        • medial hinge fracture
    • Varus producing femoral osteotomy
      • approach
        • lateral opening wedge femoral osteotomy
          • lateral subvastus approach to distal femur
        • medial closing wedge femoral osteotomy
          • medial subvastus approach to distal femur
      • technique
        • lateral opening wedge femoral osteotomy
          • k-wires inserted from lateral to medial at supracondylar femur
          • leave 1-2cm medial cortical hinge
          • spread osteotomy open and place premeasured spacer followed by lateral femoral plate
        • medial closing wedge femoral osteotomy
          • osteotomy site is at metaphyseal-diaphyseal junction
          • medial distal femoral locking plate after closure
      • complications
        • quadriceps tendon injury
        • intercondylar femur fracture
          • if osteotomy too distal
        • lateral hinge fracture
          • less stability of osteotomy after fixation
    • Gradual limb lengthening
      • approach
        • lateral hip approach for intramedullary nailing vs. external fixation
      • technique
        • distraction osteogenesis
          • wait 5-7 days to begin distraction then distract at about 1 mm/day
          • external fixator
            • uniplanar vs. circular/hexapod frame
          • intramedullary device +/- external fixator
            • insertion of intramedullary device to isthmus followed by osteotomy and completion of intramedullary nailing
            • can add external fixator for improved multiplanar stability if also trying to correct angular deformity
            • new intramedullary nails allow controlled lengthening
      • complications
        • external fixator
          • pin site infection
          • scarring
          • poor cosmesis
        • intramedullary lengthening
          • poor regenerate bone formation
          • joint contracture/dislocation
          • nail failure
    • TKA
      • approach
        • standard medial parapatellar
      • technique
        • goal is to restore neutral mechanical alignment with bone cuts of distal femur and proximal tibia
          • valgus cut angle of distal femur from 4-7º based on stature and femur length
            • intramedullary guide based on AAF
          • AAT usually equal to MAT so intramedullary/extramedullary guides usually provide equivalent resection
        • with extra-articular malalignment, same rules of normal limb deformity assessment apply
          • locate CORA on tibia, femur or both
          • as CORA moves further from knee joint, correction ability with distal femur and proximal tibia bone cuts lessens
            • more severe deformity or deformity closer to the joint may require corrective extra-articular osteotomy in addition to TKA
              • applies in both coronal and sagittal planes
              • corrective osteotomy better tolerated on tibia if necessary, as this equally alters flexion/extension gap
              • important to understand location of osteotomy, as this may affect collateral stability
                • if collateral stability compromised by ostetotomy, implant constraint should be increased
      • complications
        • periprosthetic infection
        • ligamentous contractures/laxity
        • patellar tendon injury
  • Complications
    • Deformity undercorrection/overcorrection
      • unfavorable loading on one compartment
      • preoperative planning important to avoid this
      • opening wedge osteotomy may be at higher risk because it can lose some correction over time
    • Nonunion
      • reported rates around 5%
      • risk factors
        • smoking
        • older age > 60
        • obesity
        • far cortex hinge fracture
    • Ligamentous/tendon damage
      • quadriceps tendon more at risk in femoral osteotomies
      • patellar tendon at risk in tibial osteotomies
    • Patella baja
      • caused by proximal tibia osteotomies
        • supra-tubercle osteotomy increases risk compared to infra-tubercle
      • may cause increased knee pain and difficulty with future TKA
    • Infection
      • 1-4% incidence
      • increases risk of nonunion
      • risk factors
        • smoking
        • admission to hospital vs. outpatient surgery center
  • Prognosis
    • Within first 5 years, radiographic and clinical outcomes remain excellent in >90% of patients. After >10 years, this drops to around 50-70%
      • 15-25% end up requiring TKA within 10 years
      • risk factors for poorer outcomes
        • prior failed arthroscopic treatment
        • obesity
        • age > 60
        • insufficient correction

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