Guided Growth / Hemiepiphysiodesis (Tension-Band Plating)

Indication. A child with a progressive pathological angular limb deformity — most often genu valgum or genu varum around the knee — with significant growth remaining, in whom conservative observation or non-operative care is no longer appropriate. Guided growth gradually corrects the deformity by tethering one side of an open physis so the opposite side keeps growing, swinging the limb back towards a neutral mechanical axis. Strong indications - Progressive pathological angular deformity (genu valgum or varum) with significant growth remaining (rule of thumb: at least 12 to 18 months of growth).

• Mechanical axis deviation beyond physiological limits for age, causing symptoms or documented progression.
• Blount disease (infantile and adolescent tibia vara) with an open, viable physis.
• Metabolic or rachitic deformity (for example hypophosphataemic rickets) once medical control is optimised.
• Sagittal-plane deformity — fixed knee flexion (anterior distal femoral plating) in cerebral palsy or dysplasia. Relative indications include post-traumatic partial physeal injury producing progressive angulation (with sufficient remaining physis), skeletal dysplasia (for example achondroplasia, multiple epiphyseal dysplasia) with symptomatic malalignment, asymmetric deformity at multiple levels (combined femoral and tibial plating), and mild leg-length asymmetry combined with angular deformity. Contraindications - Absolute — a closed or near-closed physis: there is no growth engine to drive correction, so the deformity persists and the family is misled; perform an osteotomy instead. Active infection at the operative site is the other absolute contraindication.
• Relative — physiological genu valgum or varum (a normal developmental variant to observe; physiological valgum peaks around 3 to 4 years and resolves), uncontrolled metabolic bone disease (correct the rickets first — the physis will not respond reliably), and a very stiff or abnormal physis (severe Blount, established physeal bar) where the response is unpredictable — counsel on slower correction and rebound. Consent specifically for the need for close follow-up and a second operation to remove the hardware, the risk of overcorrection if removal is delayed, rebound after removal (especially in young and pathological physes), incomplete correction if insufficient growth remains, implant prominence or irritation, infection, and the small risk of physeal injury from screw misplacement. The key principle — growth modulation, not correction at surgery. Guided growth does not acutely correct the deformity on the table. 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 neutral. The correction is therefore biological and time-dependent, proportional to the growth rate of the involved physis and the remaining growth — which is why it cannot work at skeletal maturity and why surveillance matters as much as the operation itself. Setup. Supine on a radiolucent table with a sandbag or bump under the ipsilateral hip to control rotation. The image intensifier must be available and tested in both AP and lateral planes before draping. A thigh tourniquet is optional — many surgeons avoid it for these small extraperiosteal exposures. Standing full-length (hip-to-ankle) alignment radiographs are reviewed pre-operatively to measure mechanical axis deviation, mLDFA and MPTA, and to identify the CORA and decide which physis (or both) to plate and on which (convex) side.

The goal: place a flexible two-hole tension-band plate extraperiosteally across one side of an open physis, with one screw cleanly in the epiphysis and one in the metaphysis, so that the tethered side slows while the open side keeps growing — gradually correcting the deformity. The exposure is small and gentle, but it is precise work under fluoroscopy: the whole game is localising the physis exactly and keeping both screws clear of it.

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Rehabilitation & surveillance | Phase | Timing | Activity & immobilisation | Monitoring | |-------|--------|---------------------------|------------| | Early | Day 0 to 6 weeks | Weight-bear as tolerated; no rigid immobilisation; simple dressing; simple analgesia (paracetamol with or without an NSAID) | Review at 6 weeks — wound check, confirm mobilisation, baseline post-op alignment film | | Surveillance | Every 3 to 4 months | Full activity | Standing long-leg alignment radiographs; track the mechanical axis and screw divergence | | Removal | When neutral | Day-case plate removal | Prompt removal the moment the mechanical axis is neutral | | After removal | To skeletal maturity | Full activity | Continue alignment surveillance — watch for rebound | Surveillance is the defining feature. Review every 3 to 4 months with standing long-leg alignment radiographs, tracking the mechanical axis and watching the screws diverge as correction proceeds. Younger, fast-growing children must be reviewed more frequently — the distal femur corrects at roughly 9 to 10 mm per year, so it corrects and overshoots fast. Pathological physes (Blount, rickets, dysplasia) correct more slowly and less predictably; optimise metabolic disease throughout. Timely removal is the most important decision in the whole pathway. 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, which is the basis of reversibility. Do not discharge at removal — continue alignment surveillance to skeletal maturity, because rebound (partial recurrence) can occur, particularly in young children and pathological physes, and may require a second episode of guided growth.

Why guided growth is different — reversibility - 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 with permanent epiphysiodesis — the deliberate, irreversible ablation of a physis used for limb-length discrepancy (a separate indication, timed by growth-prediction methods).
• And with corrective osteotomy — an acute bony correction for the mature skeleton, or for severe or rapidly progressive deformity where no growth remains. Complications

Background. Angular limb deformity in a child is common, but most is physiological — physiological genu varum in the toddler resolves, and physiological genu valgum peaks around 3 to 4 years before resolving. Guided growth is reserved for progressive pathological deformity with growth remaining. Understanding the physis and the Hueter-Volkmann principle is what makes the technique rational. The physis (growth plate). A cartilaginous disc responsible for longitudinal growth. Its zones, from the epiphyseal to the metaphyseal side, are: | Zone | Function | Vulnerability | |------|----------|---------------| | Reserve (germinal) | Stem and resting chondrocytes, matrix storage | Nutrient supply from epiphyseal vessels | | Proliferative | Chondrocyte division, longitudinal stacking | Site of active growth — drives correction | | Hypertrophic | Chondrocyte enlargement, matrix calcification | Weakest zone — the plane of Salter-Harris fractures | | Provisional calcification or metaphysis | Ossification, vascular invasion | Metaphyseal blood supply | 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, and the screws diverge over time on imaging — the sign the construct is working. Because the physis is neither compressed circumferentially nor crossed, growth resumes after hardware removal (reversibility). Growth rates (approximate — central to planning): | Physis | Approximate growth rate | Contribution | |--------|------------------------|--------------| | Distal femur | About 9 to 10 mm per year | Fastest lower-limb physis — corrects quickest | | Proximal tibia | About 6 mm per year | Common site for varus (Blount) correction | | Proximal femur | About 3 mm per year | Minor contributor to length | | Distal tibia | About 5 mm per year | Ankle valgus correction (medial malleolar plating) | A faster physis means faster correction — and faster overcorrection — so review fast-growing and young children more often. The correction rate also depends on the distance of the plate from the joint and on the health of the physis (idiopathic is faster than pathological). Deformity analysis — planning at the CORA. The CORA (centre of rotation of angulation) is the intersection of the proximal and distal mechanical or anatomical axis lines — the true apex of the deformity. For genu valgum the apex is usually at the distal femur (an abnormal mLDFA) — plate the medial distal femoral physis. For genu varum or Blount the apex is usually at the proximal tibia (an abnormal MPTA) — plate the lateral proximal tibial physis. Combined femoral and tibial deformity may both need plating. Always plate on the convex (longer) side over the responsible physis.

Key evidence. Stevens (2007) described the non-locking extraperiosteal two-hole tension-band plate ("eight-Plate") for guided growth — a flexible construct relying on the tension-band principle rather than physeal compression, hinging open as growth proceeds; 32 of 34 patients corrected to neutral, correction roughly 30 percent faster than stapling, with no permanent growth arrests. The flexible construct avoids the compression across the whole physis seen with staples, reducing the risk of permanent arrest and allowing the physis to recover after removal. The rigid Blount staple (Blount and Clarke, 1949) was the historical standard but carried higher rates of implant extrusion, breakage, migration and unintended permanent arrest. Stevens and Klatt (2008) directly documented 45 percent staple migration and 41 percent rebound, contrasted with no migration in the plate cohort — which is why plating has largely superseded stapling. Idiopathic versus pathological physes. Idiopathic genu valgum or varum corrects predictably and relatively quickly — Ballal and colleagues reported correction significantly faster in children under 10 years (p equals 0.05), with only one rebound and no permanent tethers. Blount, rickets and skeletal dysplasia correct more slowly, less completely, and rebound more often — these patients need closer surveillance and counselling about repeat procedures. In early-onset Blount disease, however, tension-band plating nonetheless improved Langenskiold stage and mechanical-axis alignment in most limbs (Hanstein and colleagues, 2023) and is now advocated as first-line surgical treatment.

Further reading - Blount WP, Clarke GR (1949). Control of bone growth by epiphyseal stapling: a preliminary report. Journal of Bone and Joint Surgery (American) 31A(3):464 to 478 — the original description of physeal stapling for growth control; the historical comparator superseded by tension-band plating.

• Paley D (2002). Principles of Deformity Correction. Springer — the reference text on CORA-based deformity analysis (mechanical axis, mLDFA, MPTA) underpinning level selection for guided growth.