Guided Growth / Hemiepiphysiodesis (Tension-Band Plating)

Surgical Indications

Absolute / Strong Indications

• Progressive pathological angular deformity (genu valgum or varum) with significant growth remaining
• Mechanical axis deviation beyond physiological limits for age, causing symptoms or progression
• Blount disease (infantile and adolescent tibia vara) with an open, viable physis
• Metabolic/rachitic deformity (e.g. hypophosphataemic rickets) once medical control is optimised
• Sagittal-plane deformity — fixed knee flexion (anterior distal femoral plating) in cerebral palsy / dysplasia

Relative Indications

• Post-traumatic partial physeal injury producing progressive angulation (with sufficient remaining physis)
• Skeletal dysplasia (e.g. achondroplasia, multiple epiphyseal dysplasia) with symptomatic malalignment
• Asymmetric deformity at multiple levels (combined femoral and tibial plating)
• Mild leg-length asymmetry combined with angular deformity (deformity-led correction)

Contraindications

Absolute:

• Closed or near-closed physis / skeletal maturity — no growth engine; perform an osteotomy instead
• Active infection at the operative site

Relative:

• Physiological genu valgum/varum (normal developmental variant — observe; valgum peaks ~3-4 years)
• Uncontrolled metabolic bone disease (correct rickets first — physis will not respond reliably)
• Very stiff/abnormal physis (severe Blount, bar) where response is unpredictable — counsel on slower correction and rebound

Key Principle — Growth Modulation, Not Correction at Surgery

Guided growth does not acutely correct deformity. It tethers one side of an open physis (the convex/longer side over the deformity apex) so that the untethered side continues to grow, gradually swinging the limb back towards a neutral mechanical axis. The correction is therefore biological and time-dependent, proportional to the growth rate of the involved physis and the remaining growth.

Evidence Base

Tension-Band Plating (Stevens)

• Stevens PM (2007): Original prospective description of the non-locking extraperiosteal two-hole tension-band plate ("eight-Plate") for guided growth — a flexible construct that relies on the tension-band principle rather than physeal compression, hinging open as growth proceeds. 32 of 34 patients corrected to neutral, correction roughly 30% faster than stapling, with no permanent growth arrests.
• The flexible construct avoids the compression across the whole physis seen with staples, theoretically reducing the risk of permanent physeal arrest and allowing the physis to recover after removal.

Tension-Band Plate vs Blount Staple

• Blount & Clarke (1949): Original description of physeal stapling for growth control — historically the standard, but associated with implant extrusion, breakage, migration and unintended permanent arrest.
• Comparative series report lower implant failure and extrusion and a more reversible effect with tension-band plates than with rigid staples; Stevens & Klatt directly documented 45% staple migration and 41% rebound, contrasted with no migration in the plate cohort. This is why plating has largely superseded stapling for temporary hemiepiphysiodesis.

Idiopathic vs Pathological Physes

• Idiopathic genu valgum/varum corrects predictably and relatively quickly (Ballal et al. reported correction faster in children under 10 years).
• Blount, rickets and skeletal dysplasia correct more slowly, less completely, and rebound more often — patients require closer surveillance and counselling about repeat procedures. In early-onset Blount disease, tension-band plating nonetheless improved Langenskiold stage and mechanical-axis alignment in most limbs and is now advocated as first-line surgical treatment.

The Physis (Growth Plate)

Zonal Architecture (epiphysis to metaphysis)

The physis is a cartilaginous disc responsible for longitudinal growth. Its zones, from epiphyseal to metaphyseal side, are:

Hueter-Volkmann principle: Compression across a physis slows growth; reduced load accelerates growth. Tethering one side mechanically modulates growth on that side — the biomechanical basis of guided growth.

Why a Tension Band Works

• A flexible plate fixed by one epiphyseal and one metaphyseal screw spans the physis on the convex side.
• The plate resists separation of the two screws on that side, slowing growth there, while the opposite (open) side grows normally.
• As the open side grows, the limb angulates back towards neutral; the screws diverge over time on imaging — a sign the construct is working.
• Because the physis itself is neither compressed circumferentially nor crossed, growth resumes after hardware removal (reversibility).

Growth Rates (approximate, important for planning)

• Faster physis = faster correction = faster overcorrection — review fast-growing/young children more often.
• Correction rate also depends on the distance of the plate from the joint and on the health of the physis (idiopathic faster than pathological).

Deformity Analysis — Planning at the CORA

• CORA (centre of rotation of angulation): the intersection of the proximal and distal mechanical/anatomical axis lines — the true apex of the deformity.
• Genu valgum: apex usually at the distal femur (abnormal mLDFA) — plate the medial distal femoral physis.
• Genu varum / Blount: apex usually at the proximal tibia (abnormal MPTA) — plate the lateral proximal tibial physis.
• Combined: femoral and tibial deformity may both need plating.
• Always plate on the convex (longer) side of the deformity over the responsible physis.

Positioning and Preparation

Patient position: Supine on a radiolucent table. Sandbag/bump under the ipsilateral hip to control rotation. Image intensifier available and tested in both AP and lateral planes before draping. Tourniquet optional (thigh) — many surgeons avoid it for these small extraperiosteal exposures.

Pre-operative planning: Standing full-length (hip-to-ankle) alignment radiograph. Measure mechanical axis deviation, mLDFA and MPTA, and identify the CORA. Decide which physis (or both) to plate and on which (convex) side.

Consent: Counsel specifically about the need for close follow-up and a second operation to remove hardware, risk of overcorrection if removal is delayed, rebound after removal (especially in young/pathological physes), incomplete correction if insufficient growth, implant prominence/irritation, infection, and the small risk of physeal injury from screw misplacement.

Tension-Band Plate Insertion — Step-by-Step

Step 1: Localise the Physis with Fluoroscopy

Use the image intensifier to identify the target physis precisely. Mark the skin over the physis on the convex side of the deformity. The plate central hole sits over the physis, with screw trajectories diverging into epiphysis and metaphysis.

Step 2: Approach and Extraperiosteal Exposure

Make a small longitudinal incision centred over the physis on the convex side. Dissect down to bone. Crucially, the plate is placed extraperiosteally — preserve the periosteum and perichondrial ring; do NOT strip the periosteum over the physis (stripping itself can stimulate or arrest growth).

Step 3: Position the Plate and Insert the Guide Wire

Place the plate so its central hole/eyelet lies over the physis. Insert the central guide wire along the physis under fluoroscopy to mark the level. Confirm in AP and lateral that the plate straddles the physis with screw paths diverging away from it.

Step 4: Insert the Epiphyseal and Metaphyseal Screws

Insert the epiphyseal screw first (the more critical, with less bone purchase), then the metaphyseal screw, each through the plate holes parallel to the physis but on their respective sides. Use cannulated self-tapping screws over guide wires. The two screws should converge slightly towards the plate but never cross the physis.

Step 5: Confirm Construct and Close

Take final AP and lateral fluoroscopic images: plate centred on the physis, both screws clear of the physis, no joint penetration. Irrigate. Close periosteal/soft-tissue layer loosely, then skin. Apply a simple dressing — no rigid immobilisation is usually required.

Step 6: Decide on Number of Physes/Sides

For isolated femoral genu valgum, a single medial distal femoral plate may suffice. For combined femoral and tibial deformity, plate both. Bilateral deformity can be addressed in the same sitting. Document exactly which physes were plated for follow-up planning.

The Critical Post-operative Phase — Monitoring and Removal

Step 7: Surveillance (the part trainees forget)

• Review at 6 weeks (wound, mobilisation), then every 3-4 months with standing long-leg alignment radiographs.
• Track the mechanical axis and watch the screws diverge as correction proceeds.
• Faster-growing/younger children: review more frequently — they correct and overshoot quickly.

Step 8: Timely Removal (and possible reversal)

• Remove the plate PROMPTLY once the mechanical axis is neutral — leaving it in causes overcorrection in the opposite direction.
• After removal, the physis resumes symmetric growth (reversibility). Continue follow-up because rebound (recurrence) can occur, especially in young children and pathological physes — a further episode of guided growth may be required.

Post-operative Protocol

Early Phase (Day 0 - 6 weeks)

• Weight-bearing: Most children weight-bear as tolerated immediately — no rigid immobilisation usually required for a tension-band plate
• Dressing: Simple wound dressing; mobilise the knee early
• Analgesia: Simple analgesia (paracetamol +/- NSAID); opioids rarely needed
• First review: 6 weeks — wound check, confirm mobilisation, baseline post-op alignment film

Surveillance Phase (the defining feature of guided growth)

• Standing long-leg alignment radiographs every 3-4 months
• Track the mechanical axis and the divergence of the screws (a marker that the tether is working)
• Younger / fast-growing children: review more frequently — distal femur (~9-10 mm/yr) corrects and overshoots fast
• Pathological physes (Blount, rickets, dysplasia): expect slower, less predictable correction; optimise metabolic disease throughout

Timely Removal

• Remove the plate PROMPTLY once the mechanical axis is neutral — this is the most important decision in the whole pathway
• Delayed removal = overcorrection in the opposite direction
• After removal the physis resumes symmetric growth — the basis of reversibility

Continued Follow-up After Removal

• Do NOT discharge at removal — continue alignment surveillance to skeletal maturity
• Rebound (partial recurrence) can occur, particularly in young children and pathological physes — may require a second episode of guided growth

Reversibility — Why Guided Growth Is Different

• The flexible tension-band construct tethers one side of the physis without compressing or crossing it; after removal the previously slowed side resumes growth.
• This contrasts sharply with:
  • Permanent epiphysiodesis — deliberate, irreversible ablation of the physis, used for limb-length discrepancy (a separate topic and indication).
  • Corrective osteotomy — acute bony correction for the mature skeleton or severe/rapid deformity where no growth remains.

Special Case: Blount Disease (Tibia Vara)

• Infantile Blount (onset under ~3-4 years) and adolescent Blount — pathological proximal medial tibial physis producing varus.
• Guided growth (lateral proximal tibial tension-band plate) can be effective in early disease with an open, viable physis (typically Langenskiold I-III).
• Advanced disease with a depressed medial plateau, bar, or severe deformity (higher Langenskiold stages) often needs osteotomy (+/- physeal bar resection).
• Higher rebound and slower correction than idiopathic deformity — counsel families and continue surveillance.

Special Case: Rickets / Metabolic Bone Disease

• Optimise medical management first (e.g. phosphate and active vitamin D in hypophosphataemic rickets) — an uncontrolled rachitic physis responds poorly and recurs.
• Guided growth can correct deformity while medical control continues, but expect slower correction and higher recurrence; combined femoral + tibial plating is often needed.

Special Case: Sagittal-Plane Deformity (Fixed Knee Flexion)

• Anterior distal femoral guided growth (anterior plating) can gradually correct fixed knee flexion (e.g. in cerebral palsy), exploiting the same Hueter-Volkmann principle in the sagittal plane.
• Same prerequisites apply: open physis, adequate growth, close monitoring, timely removal.