Table 1.

Paley’s level of difficulty score [4]

Points scored	0	1	2	3
Age	5–19	20–29, 0–4	30–50	>50
Complexity of correction of deformity at level of lengthening	None	Angulation >5° <20° Rotation >10° <30° Translation <50 % or change of mechanical axis 1–3 cm	Angulation ≥20° Rotation ≥30° Translation ≥50 % or change of mechanical axis >3 cm	Combination of deformities at one level or multilevel deformity
Other levels of treatment in same bone	None	1 Additional level, mild complexity	1 Additional level, moderate complexity	1 Additional level, severe complexity or ≥addition
Associated tibial lengthening (cm)	None	1–3	3.1–6	>6
Instability of joint	None	Grade I—mild instability: anteroposterior instability of knee with end point. Shenton’s line not broken	Grade II—moderate instability: anteroposterior instability of knee without end point. Shenton’s line broken but reducible	Grade III—fixed subluxation or dislocation
Fixed flexion deformity of knee (°)	0	1–5	6–20	>20
Flexion of knee (°)	>120	100–120	65–99	<65
Osteoarthrosis of joint	None	Marginal osteophytes, subchondral sclerosis	Narrowing of joint space	Loss of joint space (bone on bone)
Quality of bone	Normal	Ollier’s disease, mild osteoporosis, non-union	Radiation, neurofibromatosis, osteogenesis imperfecta	Osteonecrosis, infection
Quality of soft tissue	Normal	Spastic, obese, muscular	Fibrotic, post-radiation, small open wound	Tissue necrosis, infection, large open wound
Medical problems and medications	None	Smoking, hypertension, rheumatoid arthritis or other systemic arthritis	Diabetes, haemophilia, sickle cell anaemia, mild immunosuppression, bone-inhibition medication	Moderate immunosuppression, anti-metabolic chemotherapy