Coxa Vara

Key Concepts:

• The deformity is in the NECK, not the head or shaft.
• It is a progressive dysplasia if untreated.

• Presenting Complaint: "Painless limp".

  • Age: Usually noted after walking begins (2-5 years).
  • Pain: Rare in childhood. If pain is present, suspect stress fracture or superimposed pathology.
  • Family History: Ask about siblings or parents (hip issues).

  History of premature hip replacement in parents is a clue.

The evidence cards target not only the HE angle but the head-shaft (HS) angle — Desai aimed for a postoperative HS angle of 130 degrees or more — yet this is a distinct measurement the topic relies on but never defines.

• Why the neck-shaft angle is unreliable in coxa vara. The standard neck-shaft angle is drawn from the femoral-shaft axis to the femoral-neck axis. In coxa vara the neck itself is short, bent and often carries an ossification defect, so a reproducible "neck axis" is hard to draw and the NSA becomes unreliable.
• The head-shaft angle avoids this by measuring from the femoral-shaft axis to a line along the base of the capital epiphysis / through the head, rather than the deformed neck — so it reports the true head-on-shaft orientation independent of neck shape.
• How the three angles work together:
  • HE (Hilgenreiner-epiphyseal) angle — physeal obliquity; the shear/prognosis measure that decides whether to operate (over 60 degrees = operate).
  • Head-shaft angle — the corrected head-shaft geometry; a surgical target (aim for about 130 degrees or more, per Desai).
  • Neck-shaft angle — the classic definition (under 120 degrees) but the least reproducible once the neck is deformed.
• Practically: use the HE angle to decide whether to operate and the head-shaft (with HE) angle to judge how much you corrected. Desai's durable-result target was an HE angle of 35 degrees or less and a head-shaft angle of 130 degrees or more.

Coxa vara repeatedly runs into the greater trochanter — Viva 4 asks about "trochanteric advancement if the GT is very high", the Desai series found trochanteric overgrowth with abductor weakness in 5 of 12 hips, the "articulo-trochanteric distance" is a named measurement, and premature capital-physis closure yields a short neck (coxa breva) with a relatively high trochanter. Here is the concept those references rely on.

• Why the trochanter matters. The abductors act through the lever arm from the hip centre to the greater trochanter. In coxa vara the short/varus neck plus trochanteric overgrowth brings the trochanter up to or above the centre of the femoral head, shortening the abductor lever arm and slackening the muscle — the mechanical basis of the Trendelenburg gait that can persist even after the neck angle is corrected.
• Measuring it — the articulo-trochanteric distance (ATD). The ATD is the vertical distance from the tip of the greater trochanter to the top of the femoral head on an AP film (normally the head sits roughly 1 to 2 cm above the trochanter tip). A reduced, zero or negative ATD (trochanter at or above the head) quantifies trochanteric overgrowth and abductor insufficiency.
• Two mechanisms:
  • Absolute overgrowth — the trochanteric apophysis keeps growing while the capital physis is arrested (classically after premature capital-physis closure, giving coxa breva), so the trochanter overtakes the head.
  • Relative overgrowth — the neck is simply short/varus, so the normally-growing trochanter sits relatively high.
• What to do about it:
  • Distal (and lateral) trochanteric advancement/transfer — osteotomise the greater trochanter and move it distally to restore abductor length-tension and the lever arm; used for the high trochanter in an older child or after coxa breva.
  • Greater trochanteric (apophyseal) epiphysiodesis — in a young child with growth remaining, arresting the trochanteric apophysis lets the neck "catch up" and prevents future overgrowth.
  • This is exactly why the surgical warnings stress protecting the trochanteric apophysis: iatrogenic arrest tips the neck-trochanter balance the wrong way.

• Natural History:
  • HEA less than 45: 80% spontaneous resolution.
  • HEA greater than 60: 100% progression. untreated leads to severe shortening, limp, and early OA.
• Surgical Outcomes:
  • Success Rate: 90% correction if adequate valgus achieved.
  • Limp: Usually resolves if biomechanics are restored.
  • Leg Length: Osteotomy lengthens the leg (valgus gain), but pre-existing physeal arrest may result in permanent shortening (0.5 - 2 cm).
• Long Term:
  • Even with correction, the hip is rarely "normal".
  • Acetabular dysplasia usually remodels if head is centered.
  • Mild risk of OA remains.

Global Epidemiology:

• Developmental/congenital coxa vara is rare (~1 in 25,000 live births) and far less common than DDH.
• Reported across all populations; some series describe higher frequency in populations of African descent and in Scandinavian cohorts (echoing the distribution of Blount disease).
• Often diagnosed late once the child is walking; delayed presentation is most marked in limited-resource and rural settings.

Guideline & Consensus Position (side by side):

There is broad international agreement: the HE angle drives the decision and valgus intertrochanteric osteotomy is the definitive operation. Differences are largely in implant preference and timing.

Registry & Implant Notes:

• No dedicated paediatric coxa-vara registry exists; this is a rare deformity managed in tertiary centres rather than tracked at population scale.
• Pediatric proximal femoral locking compression plates (LCP) have largely replaced fixed-angle blade plates in many units for ease of application; published series report high but reliable hardware-removal rates for trochanteric irritation.
• Fixed-angle blade plates remain a robust, low-cost option and are still widely taught.

High- vs Limited-Resource Practice Variation:

• High-resource: 3D CT planning for combined varus/version correction, image intensifier-guided osteotomy, modern locking implants, early mobilisation.
• Limited-resource: Reliance on plain radiographs and templating; blade plates or even smooth wires with hip spica for fixation; later presentation means larger corrections and more frequent need for concomitant trochanteric advancement.
• Across all settings, the principle is identical — overcorrect to valgus, restore a near-horizontal physis, and protect the construct until union.