Instrument 07Own reference

Pre-op instrument · spine

Two spines, the same films. One needs half the correction.

Put identical radiographs into this tool twice and change only the age. At seventy-eight the age-adjusted target asks for twenty-six degrees of lordosis. At thirty-four it asks for fifty-three. Correcting the older spine to the younger number is not thoroughness. In the cited series it is precisely the overcorrection that separated the patients who developed junctional kyphosis from those who did not.

Signature

26.3° vs 53.5°

Correction demanded of identical films at 78 and at 34. A 27° swing on age alone.

Fig. 1 · The same films, twenty-seven degrees apart

One universal target is wrong in both directions and dangerous in only one. Overshooting the elderly is the direction associated with junctional failure.

Measure this spine → See the two identical spines →

The same spinopelvic films the hip page uses, read in the opposite direction

Read this first, and it is louder here than anywhere else in this programme. Adult spinal deformity planning is a subspecialty discipline and the consequences of a wrong target are severe. The age-adjusted values in this tool are reproduced as approximate brackets, to demonstrate the shape of the relationship — every target loosens with age. They are not a substitute for the primary publication, and the exact regression must come from it before anything here informs an operation. Reported correlations between junctional kyphosis angle and the offset from the age-adjusted objective were small, around 0.32 for the lordosis mismatch. The direction is supported. The precision is not. This page models a principle, not a plan.

The envelope · standing full-length lateral, femoral heads visible

The same numbers the hip page uses, asked in the opposite direction.

The hip page measures spinopelvic parameters to decide where to put a cup, and treats a stiff spine as a hazard to plan around. This page measures the same parameters to decide what to fuse — which is the operation that creates the stiff spine the hip page is worried about. One system, two ends, and the age of the person in front of you decides the target at both.

The person

The single input that moves the target most.

Age78

Junctional kyphosis rises from about 18% in young adults to about 50% in the elderly.

Pelvic incidence65°

Fixed morphology. It does not change with posture or with your operation.

Lumbar lordosis22°

The parameter you are actually going to change.

The rest of the sagittal picture

The other two SRS-Schwab modifiers.

Sagittal vertical axis115 mm

0 under 40 mm, + to 95 mm, ++ beyond.

Pelvic tilt34°

0 under 20°, + from 20 to 30°, ++ above 30°.

Age bracket in use

75+

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Tier D

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The number this page exists to show

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Log this spine →The two identical spines →

The finding

Identical radiographs. A twenty-seven degree swing in what they demand.

These two patients have the same pelvic incidence, the same lordosis, the same sagittal vertical axis, the same pelvic tilt, and the same marked modifiers across all three. Nothing on the film distinguishes them. Only the date of birth does, and it moves the target by more than the deformity of many of the patients on this list.

	78 years old	34 years old
Pelvic incidence minus lordosis	43°	43°
Sagittal vertical axis	115 mm	115 mm
Pelvic tilt	34°	34°
SRS-Schwab modifiers	++ / ++ / ++	++ / ++ / ++
Age-adjusted lordosis target	16.7°	−10.5°
Correction the age-adjusted target asks for	26.3°	53.5°
Correction a neutral target would ask for	43°	43°
Extra correction the textbook demands	16.7° too much	10.5° too little

The asymmetry is the point. In the older patient a neutral target overshoots by nearly seventeen degrees, in the age group where junctional kyphosis already runs near fifty percent and where the cited analysis found that the patients who failed were the ones who had been overcorrected. In the younger patient the same neutral target undershoots. A single ideal number is wrong in both directions; it is only dangerous in one of them.

The numbers, and how firm each one is

Firm classification. Softer targets. Small correlations.

The classification

0 / + / ++

Three sagittal modifiers. Pelvic tilt is 0 under 20°, + from 20 to 30°, ++ above 30°

Junctional kyphosis by age

18 → 44 → 50%

Young adult, middle-aged, elderly. It rises steeply and the elderly rate is close to a coin flip

And who it happened to

overcorrected

Patients who developed it had been overcorrected relative to age-adjusted goals, by about 5.2° of lordosis mismatch

Independently reported

increases

Overcorrecting lordosis relative to pelvic incidence, judged against the age-adjusted ideal, tends to increase junctional kyphosis

How tight the relationship is

r ≈ 0.32

The correlation between junctional angle and offset from the age-adjusted objective was small. Direction yes, precision no

This one IS in the mandate

TEAM

Spinal fusion is one of the five episode categories. Mandatory since 1 January 2026

What this model cannot see. Junctional kyphosis is multifactorial: bone quality, the upper instrumented vertebra, the fixation used, soft-tissue handling and frailty all matter, and none of them are inputs here. A tool that reduces it to one alignment offset is showing you one contributor, not a risk score. Not a cleared device, not clinical advice.

Eleven joints, one structure

This page and the hip page are the same measurement.

	The hip page	This page
Films	Standing and seated lateral spinopelvic	Standing full-length lateral
Parameters	Pelvic incidence, sacral slope, tilt	Pelvic incidence, lordosis, tilt, sagittal axis
The question	Will this pelvis move?	How much of that motion am I about to remove?
A stiff spine is	A hazard to plan the cup around	The thing this operation creates
The reference	The patient’s pelvic incidence	The patient’s age

The other end

The hip.

Same films, opposite direction. A stiff pelvis collapses the cup window to a couple of degrees — and a long fusion to the pelvis is one way a pelvis gets stiff.

The hip instrument →

Where the programme started

The knee.

Measure the envelope, position first, change the implant only on what is left.

The knee instrument →

Log this spine

Put the first row in.

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Do not enter patient details: no names, dates of birth, record numbers or anything else that identifies a patient, in the note or anywhere on this page. Stored for calibration research, not as a clinical record.