Limb Deformity

Evaluation & Management

History

• General questions about how the deformity came about, timings, etc.
• Specifically:
  • Is there pain?
  • What are the functional limitations?
  • Are there signs of sepsis?

Examination

• Manual stressing of the malunion site:
  • Is it painful or does it move?
  • Solid malunion should be immobile and pain-free
• Soft tissues:
  • Amenable to further surgery
  • Signs of infection
• ROM of joint below and above:
  • Is there a compensatory deformity at the joint?
  • If so, is this fixed – will it need correction concurrently?
• Functional problems:
  • Gait
  • Simple upper limb functions
• Leg lengths – true and apparent
• Neurovascular status

X-Ray Evaluation

• Full-length weight-bearing views where possible:
  • Taken on a 51-inch cassette
• True AP and lateral films of the affected segments
• Overall Limb Alignment:
  • Mechanical axis
  • Anatomic axis
  • Deformity plane
  • Joint deformity
  • Centre of Rotation of Angulation (CORA)

Anatomic Axis

• A through the center of the diaphysis of a bone at at least 3 points
• In a deformity, each segment of bone may have a different anatomic axis

Mechanical Axis

• A line between the centre of the joints above and below a bone

Joint Orientation Lines

• Lines representing the orientation of a joint to the respective mechanical and anatomic axes of a bone
• Can tell you if there is deformity near the joint or in the diaphysis alone

Angles to Assess in Lower Limb:

• LPFA: Lateral Proximal Femoral Angle
• mLDFA: Mechanical Lateral Distal Femoral Angle
• aLDFA: Anatomic Lateral Distal Femoral Angle
• JLCA: Joint Line Congruence Angle
• MPTA: Medial Proximal Tibia Angle
• LDTA: Lateral Distal Tibia Angle
• MNSA: Medial Neck Shaft Angle

MAD (Mechanical Axis Deviation)

• Shows how far the mechanical axis of the limb has deviated from the centre of the knee
• Used for calculating the degree of varus/valgus at the knee

CORA – Centre of Rotation and Angulation

• Deformities are rarely just angular in one plane
• Usually are multiplanar with translational and rotational elements
• CORA plotting shows the COR of the deformity for correction
• CORA does not account for rotation as it is based on 2D X-rays
• CORA represents a point in space between the mechanical axes of the deformity
• CORA illustrates the necessary site of osteotomy to correct the deformity - this may be outside the bone!
• In a uniplanar angular deformity only, the CORA is at the site of apparent angulatory deformity
• When deformity is due to angulation and translation, the CORA will not be at the site of apparent angulation

Bissector

• The Bissector is a line that bisects the CORA and the angle formed by the two mechanical axes that create the deformity
• Any point along the bisector is effectively a CORA because correction along the bisector will correct the deformity
• The further along the bisector, away from the CORA the osteotomy is made, the larger the opening required to correct the deformity

Saggital Plane Deformity

• Better tolerated therefore more priority is given to AP deformity
• All the same angles can be plotted in the saggital plane

Rotatory Deformity

• Measurement is difficult
• Best way is probably clinically using rotational profiles
• Axial CT or MRI is another alternative
• Is rotation causing a functional problem?
  • <10 degrees usually poorly tolerated

Clinical Assessment of Rotation

Tibial Malrotation

• Use the line of the foot (2nd toe to centre of calcaneus) compared to either the tibia or femur of both legs
• If using femur, patient prone or sat with knees flexed at 90 degrees
  • Look at deviation of foot away from the femoral axis
  • Foot axis, tibia axis, and femoral mechanical axis should all be in one line
• If using the tibia, patient stands with patellae pointing forwards
  • Assess the deviation of the foot away from the axis of the tibia

Femoral Malrotation

• Patient prone, knees at 90 degrees and femoral condyles parallel to couch
• Passively internally & externally rotate hips
  • Observe the degree of excursion of the tibiae between the two legs
• Beware of a concurrent tibial angulatory deformity, which can cause an apparent femoral angulatory deformity

Upper Limb Deformity

• Same principles but in general deformities are better tolerated

General Principles of Treatment

Order of Correction

• Angulation > Translation > Length > Rotation > +/- Translation again
• Correction of rotation may cause another translatory deformity, which will need correcting again

Soft Tissues

• Are the soft tissues amenable to the various corrective options?
• Where are the NV bundles in relation to the deformity?
  • If on the concave side, they will be stretched in the correction

Osteotomies

• Opening or closing wedge
• Dome
• Ideally perform osteotomy at the CORA or along the bisector
• The further along the bisector away from the CORA the osteotomy is made, the larger the opening required to correct the angulation
• Osteotomy may not be able to be performed at the CORA
• Osteotomies away from the CORA can also correct the angulation but will result in lengthening, shortening, or translation, which will then need correction
  • This is often the case in periarticular, multiplanar deformity

Methods of Correction

• Simple osteotomies with plate or IM nail fixation are good for uniplanar deformity where the CORA is at the deformity
• Ilizarov or Taylor Spatial Frame are better for multiplanar deformities and where length needs to be adjusted
  • This avoids multiple osteotomies and soft tissue violation
• Principles of defining the deformity, CORA, and Bisector are the same though

Management of Segmental Bone Defects

Causes of SBDs

• Acute high energy trauma with bone loss
• Chronic infection requiring bone debridement
• Non-union with osteolysis

Management

• Depends on:
  • Defect size
  • Location
  • Patient & surgeon factors
• Critical size defect in general terms is 2cm or more or is 50% loss of the circumference of the bone

Management Options

• Amputation
• Acute Shortening
• Massive Cancellous Autograft
• Local Fibula Graft (in tibial PTSBD)
• Masqulet Technique
• Distraction Osteogenesis
• Free Vascularized Bone Transfer

Acute Shortening

• Better tolerated in upper limb and single bone segments (humerus/femur) – up to 5cm well tolerated
• < 3cm can be tolerated in tibia if fibula comminuted

Advantages

• Provides immediate stability
• Allows healing to begin
• Relaxes soft tissues and allows for closure/grafting of soft tissue defects
• Low complication rate

Problems

• Results in limb length inequality that may require future correction (not necessarily a disadvantage)
• May leave redundant skin if excessive shortening
• Excessive shortening can compromise vasculature

Autologous Cancellous Graft

• Good osteoinduction, osteoconduction & osteogenesis.
• Still the GOLD STANDARD
• Generally felt max defect treatable is 5-7 cm
• Best graft is from iliac crest with some evidence it has biologically better properties than graft from elsewhere
• Posterior crest better because of volume but anterior preferred due to ease

RIA (Reamed Irrigation Aspirator)

• Some evidence that this produces even better quality graft than iliac crest & superior volumes (up to 68 ml)
• Eliminates graft site morbidity of crest but concerns regarding iatrogenic fractures

Advantages

• Cancellous graft still best osteoinductivity and conductivity available
• Reasonable option for smaller defects (<4cm)
• Cheap and no expertise required

Problems

• Unpredictable union

• Long time to union

• Graft site morbidity

• Should not be done primarily – always wait 6/52 > allows wounds to heal and soft tissues to revascularize after initial high energy injury > earlier grafting may contribute to infection

• Combine with freshening up bone ends by drilling medulla/burring cortical bone/excising scar tissue

• Technique in Tibia > Traditionally posterolateral with patient prone and graft from posterior iliac crest

• Lay graft around defect and on interosseous membrane to encourage a synostosis

• Be mindful of any vascularized flaps and avoid approaches that may compromise them

• Alternative approaches can be used especially in proximal tibia where PL approach endangers NV bundle

• Make sure graft overlaps by 1cm either end of defect

Masqulet Technique (Induced Membranes)

• Mainly for defects with concurrent severe soft tissue injury
• Stage 1:
  • Debride bone ends as required and insert a cement spacer
  • Soft tissue reconstruction in the meantime
  • The theory is that a synovial-like membrane, rich in blood supply and growth factors, forms around the cement block
• Stage 2:
  • Remove spacer and insert autologous cancellous graft into membrane which augments healing of the bone
  • No good quality evidence to back this
  • ? When to remove cement block
  • ? Doesn’t removal disrupt the membrane
  • Application seems to be in gaining soft tissue control prior to grafting

Distraction Osteogenesis (Bone Transport)

Advantages

• Can manage intermediate or large defects (up to 30cm reported)
• Use of frames allows soft tissue management
• Malalignment can be prevented/corrected

Problems

• Requires patient compliance
• Long process
• Pin-site infections can cause chronic infection

Techniques

• Ilizarov Frame:
  • Most commonly used
  • Allows correction of malalignment
  • Pins can cause soft tissue problems when distracted
  • Chronic infection
• Unilateral Rail Frame:
  • Less technically demanding to apply
  • ? Better tolerated by patient
  • Less control on alignment
• Lengthening Over a Nail:
  • Maintains alignment
  • Nail may interfere with regenerate and delay union
• Performing corticotomy and distracting & docking simultaneously (docking site usually grafted)
• Acutely shortening, then performing corticotomy later and distracting > tends to reduce complications
• Corticotomy should be metaphyseal (better union/regenerate rate)
• Allow a 5-day latent period for inflammatory phase of healing to begin
• Distraction should not be >1mm per day
• For each 1mm of lengthening, 2-3 days of consolidation are required
• Around 6 weeks per 1cm of defect required for healing plus normal time of bone healing
• Overall recommendation - distract using an ilizarov if expertise available, otherwise rail frame. Shorten first, then distract.

Free Vascularized Bone Transfer

• Can be rib, iliac crest or fibula but is most often Fibula
• 5cm distal and 7cm proximal must be left when harvesting to prevent ankle, knee and peroneal nerve problems
• Bury ends of fibula into bone at either end of defect and fix with screws

Advantages

• Can be used for very large defects
• High success rate in post-traumatic defects

Problems

• Graft site morbidity – chronic pain/neurogenic pain/ankle or knee instability
• Fracture if graft does not hypertrophy
• Limb must have an available artery that is not the sole supply of the limb for anastomosis
• Requires considerable expertise, cost, and time

Local Fibula Graft

• Either osteotomize fibula and fix to lateral aspect tibia or within tibia

Advantages

• Allows acute spanning of defect
• Easy to perform

Problems

• Poor muscle function
• Not always possible
• Weak and high fracture risk if does not hypertrophy

Soft Tissue Management

• All large soft tissue defects need to be managed emergently
• Ideally with free flap transfer
• Within 1 week ideal (before wound colonization)
• All bone reconstructive procedures have higher success in setting of a healed soft tissue envelope

Subchondral Defects:

• Properties required of the graft are to have high initial compressive strength and osteoconductivity
• Osteogenesis & Osteoinductivity are not as important because metaphyseal defects are known to spontaneously heal if left alone
• Therefore graft required to provide a stable articular reduction and prevent complications associated with steps/gaps
• Calcium Phosphate cement currently best graft for this purpose
  • Level 1 RCT vs autologous cancellous graft
  • Meta-analysis showed it was associated with better functional outcomes

Future Possible Methods

• Use of Bone Morphogenic Proteins and local scaffolds surgically placed
• Gene therapy

Length of Defect (cm) | Primary Treatment Option

• 0.5-3: Cancellous bone grafting
• 2-10: Bone transport
• 5-12: Free vascularized bone grafting
• 10-30: Amputation

Benefits and Drawbacks of Management Methods for Post-Traumatic Segmental Bone Defects

Treatment	Major Benefits	Major Drawbacks
Amputation	Shortest treatment time	Total loss of limb function
Limb shortening	Short treatment time; fewest complications	Some loss of limb function
Autologous nonvascularized cancellous bone graft	Generally applicable; reasonable results	Slow, unreliable consolidation; donor site morbidity; less applicable to large defects
Bone transport distraction osteogenesis	Ultimately, the best quality of bone; applicable to large defects	Frequent complications; long time to heal
Free vascularized graft	Acute fill of defect with living bone; microvascular capability; applicable to large defects	Donor site morbidity; fracture; lack of hypertrophy
Local fibula	Acute spanning of defect; donor morbidity limited; no special equipment required	Not always possible; not very strong; poor muscle function