Does earlier hip surgery actually produce better results than waiting?

Yes, and this has been demonstrated directly. One study tracking outcomes before and after a national hip surveillance guideline was introduced found the median migration percentage at the time of surgery dropped from 75% to 39% after surveillance became standard practice, and lower preoperative migration percentage was significantly linked to better results after surgery. Separately, older age at the time of surgery and higher preoperative migration percentage are both established predictors of avascular necrosis, a serious complication of hip reconstruction. Earlier, better monitored intervention is measurably safer and more effective than the same surgery performed later on a more advanced hip.

Why does age matter so much in the decision to delay or proceed with surgery?

Two separate clocks are running. The first is the neuroplasticity window: the brain's capacity to build new functional pathways in response to intensive therapy is highest in the first several years of life, so combining spasticity reducing surgery with therapy during this window tends to produce better long-term functional outcomes than the same surgery performed later. The second is structural: contractures and hip displacement become more established and harder to correct the longer they're left unaddressed. Both clocks point the same direction, toward earlier assessment being lower risk and higher benefit than indefinite delay, though not toward panic or rushing any individual family's decision.

What is a reasonable surveillance schedule if we decide to wait rather than proceed with surgery now?

For children who are able to walk independently with a low GMFCS level, a single hip X-ray in early childhood showing a normal migration percentage may be sufficient with no further monitoring needed. For children with more significant spasticity or higher GMFCS levels, hip X-rays are typically recommended every 6 to 12 months until skeletal maturity. Alongside this, periodic reassessment of spasticity itself, using tools like the Modified Tardieu Scale, and tracking whether physiotherapy is still producing functional gains, both give concrete markers for whether 'waiting' is genuinely stable or quietly progressing.

What Happens If My Child Doesn’t Have CP Surgery? Understanding the Cost of Delay

Surgical Decision-Making 13 min read

What Happens If My Child Doesn’t Have Surgery? Understanding the Cost of Delay

Q: What actually happens to a hip left untreated in cerebral palsy?

Once a hip's migration percentage, the standard measure of how much of the femoral head has shifted out of the hip socket, passes 30%, it's considered at risk, and the well documented natural history is continued displacement toward full dislocation without intervention. Between roughly 40 and 60% migration, surgical correction is typically indicated, and outcomes are generally better the earlier within that range treatment happens. Past a migration percentage of around 70%, research has found a statistically significant, nearly fourfold increase in the odds of the hip redislocating even after reconstructive surgery. In other words, delay doesn't just make the eventual surgery bigger; past a certain point it makes even successful surgical correction less reliable.

Q: Is 'wait and see' always the wrong approach?

No, and this is an important distinction. Active surveillance, meaning scheduled reassessment with actual measurements like hip X-rays or Tardieu Scale scores at defined intervals, is a legitimate and often correct clinical approach for many children, especially those with milder spasticity or lower GMFCS levels. What carries real cost is a different thing: skipping surveillance entirely, not tracking whether things are stable or progressing, and treating 'we'll revisit this later' as a decision rather than a plan with a defined next checkpoint.

Q: Does delaying surgery make the eventual procedure more invasive?

Often, yes, particularly for hip displacement. Lower migration percentages at the time of surgery are associated with less invasive procedures and better retained correction afterward, while higher migration percentages, especially above 70%, are linked to a meaningfully increased risk of the correction failing and needing to be redone. For soft tissue spasticity more broadly, a fixed contracture that has developed because dynamic spasticity was left unaddressed for years typically requires a different, more involved surgical approach than the same muscle would have needed if treated while the spasticity was still primarily dynamic.

“Let’s wait and see” is one of the most common responses to a surgical recommendation, and it’s sometimes exactly right. It’s also sometimes quietly costly in ways that only become visible years later. This article uses the best quantified evidence available, mostly from hip health, since it’s the most precisely measured, to show what waiting actually costs and when.

Written by CP Clinic Medical Team Tovmed Medical Center, Vinnytsia, Ukraine

Medically reviewed by Prof. Vigein Tovmasian PhD · Orthopedic Surgeon · Honorary Doctor of Ukraine

Why “wait and see” feels like the safe choice

It’s a completely understandable instinct. Surgery feels irreversible and frightening in a way that continuing physiotherapy doesn’t. A child who seems stable right now doesn’t feel like an emergency. And there’s a natural hope that things might simply resolve on their own, or that the child will “grow into” better function.

The honest answer is that waiting is sometimes exactly the right call, and sometimes it quietly costs more than families realise, because the cost doesn’t show up immediately. It shows up as a slightly worse starting point at the next assessment, then the one after that, until a procedure that could once have been simpler and safer has become bigger and riskier. This article is about making that trade-off visible rather than invisible.

A worked example: what the hip numbers actually show

Hip health in CP is tracked using a specific, well validated measurement: the migration percentage (MP), essentially what proportion of the ball of the hip joint has slipped out of its socket. Because it’s a number, not an impression, it gives an unusually clear picture of what “waiting” actually does over time.

Below 25 to 30%

Normal to borderline

Routine surveillance is generally all that’s needed. For children walking independently with low GMFCS levels, a single normal scan in early childhood may be enough with no further monitoring required.

30 to 40%

The hip is officially “at risk”

The well documented natural history past this point is continued displacement, not stability, without some form of intervention. This is the point where surveillance needs to tighten, not loosen.

40 to 60%

The typical surgical window

Correction is generally indicated in this range, and outcomes tend to be better the earlier within this window treatment happens rather than later.

70% and above

Even successful surgery becomes less reliable

Research has found a statistically significant, nearly fourfold increase in the odds of the hip redislocating even after reconstructive surgery once migration has reached this level. Delay here doesn’t just mean bigger surgery; it means less certain surgery.

Pooled data across population studies found roughly a third of children with CP develop hip displacement past the 30% at-risk threshold, and in non-ambulatory children specifically, progressive migration has been observed in a substantial proportion, up to 45 to 90% depending on the population studied. This isn’t a rare edge case; it’s a mainstream part of the natural history for many children with more significant spasticity, which is exactly why surveillance protocols exist in the first place.

Earlier really is measurably better, not just theoretically

This isn’t only a logical inference; it’s been demonstrated directly. One study compared outcomes before and after a national hip surveillance guideline was introduced, tracking the migration percentage recorded at the time of surgery.

Median migration percentage at time of surgery

Before surveillance guideline

75%

After surveillance guideline

39%

Lower migration percentage at the time of surgery was significantly linked to better outcomes afterward. Separately, research on complications after hip reconstruction has identified older age at surgery and higher preoperative migration percentage as established predictors of avascular necrosis, a serious complication where the blood supply to the femoral head is disrupted. Both findings point the same direction: the same surgery, performed earlier on a less advanced hip, is measurably safer and more likely to hold.

The two clocks running at once

The neuroplasticity clock

The brain’s capacity to build new functional pathways in response to intensive therapy is highest in the first several years of life. Reducing spasticity surgically during this window, then following with intensive physiotherapy, tends to produce better long-term function than delaying the same procedure into later childhood, when this capacity has naturally declined.

The structural clock

Contractures and hip displacement become more established, and correspondingly harder and riskier to correct, the longer they progress unaddressed. The hip data above is the clearest quantified example, but the same underlying logic applies to soft tissue contractures more broadly.

Neither clock is a reason to rush any individual family into a decision they’re not ready for. Both are reasons to treat “we’ll revisit this later” as something that needs a specific next checkpoint, rather than an indefinite pause.

Good waiting versus costly delay

The distinction that actually matters isn’t waiting versus not waiting. It’s monitored versus unmonitored.

Active surveillance, a legitimate approach

Hip X-rays on a defined schedule, typically every 6 to 12 months for children with significant spasticity
Periodic Modified Tardieu Scale reassessment to track whether spasticity is becoming more structural over time
A clear, specific date or milestone for the next reassessment, not an open-ended “later”
Honest tracking of whether physiotherapy is still producing functional gains, not just being attended

Unmonitored delay, where real cost accumulates

No scheduled hip X-rays, or scans that get pushed back repeatedly without a specific reason
No reassessment of whether spasticity has shifted from dynamic toward fixed
“We’ll think about it again eventually” with no defined trigger for revisiting the decision
Assuming stability without measuring it, simply because nothing dramatic has happened recently

If your family is genuinely doing the version on the left, waiting can be a perfectly reasonable, evidence-informed choice. If it’s drifted into the version on the right, that’s worth naming honestly and correcting, not because surgery is always the answer, but because an unmonitored “later” is where the quiet, measurable cost described in this article actually accumulates.

Want an honest assessment of where your child’s specific situation currently sits, and what a reasonable next checkpoint looks like?

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Frequently asked questions

What actually happens to a hip left untreated in cerebral palsy?

Past a migration percentage of 30%, the hip is considered at risk, and the documented natural history is continued displacement toward dislocation without intervention. Correction is typically indicated between 40 and 60%. Past around 70%, research found a nearly fourfold increase in the odds of redislocation even after successful reconstructive surgery, meaning delay eventually makes even surgical correction less reliable.

Does earlier hip surgery actually produce better results?

Yes, directly demonstrated. One study found the median migration percentage at surgery dropped from 75% to 39% after a national surveillance guideline was introduced, and lower preoperative migration percentage was linked to significantly better outcomes. Older age and higher preoperative migration percentage are both established predictors of avascular necrosis, a serious surgical complication.

Is “wait and see” always the wrong approach?

No. Active surveillance, meaning scheduled reassessment with real measurements at defined intervals, is legitimate and often correct for many children. What carries real cost is skipping surveillance entirely and treating “we’ll revisit this later” as a decision rather than a plan with a specific next checkpoint.

Why does age matter so much in this decision?

Two clocks run simultaneously. The neuroplasticity window, when the brain most readily builds new pathways in response to therapy, is highest early in childhood. Structurally, contractures and hip displacement become more established and harder to correct the longer they’re left unaddressed. Both point toward earlier assessment being lower risk, not toward rushing any individual decision.

What is a reasonable surveillance schedule if we choose to wait?

For independently walking children with low GMFCS levels, a single normal early scan may be sufficient. For children with more significant spasticity, hip X-rays every 6 to 12 months until skeletal maturity is standard. Alongside this, periodic Modified Tardieu Scale reassessment and honest tracking of whether physiotherapy is still producing gains both give concrete markers of whether waiting is genuinely stable.

Does delaying surgery make the eventual procedure more invasive?

Often, yes, especially for hip displacement, where lower migration percentages at surgery are linked to less invasive procedures and better retained correction, while higher percentages, especially above 70%, carry meaningfully higher failure risk. For contractures more broadly, a fixed contracture that developed from years of unaddressed spasticity typically needs a different, more involved surgical approach than the same muscle would have needed earlier.

References

“Hip displacement in children with cerebral palsy: surveillance to surgery, a current concepts review.” SICOT-J. SICOT-J ↗
“Hip Surveillance in Cerebral Palsy: The Importance of Doing It Early and Often.” Children’s Hospital of Philadelphia. CHOP ↗
Lins LAB, Watkins CJ, Shore BJ. (2019). “Natural History of Spastic Hip Disease.” Journal of Pediatric Orthopaedics. PubMed ↗
“Reimers Migration Percentage in Cerebral Palsy Hip Displacement: A Literature-Based Rationale and Statistical Optimization From a Retrospective Cohort.” PMC. PMC ↗
“Timely Surgical Intervention Leads to Better Sustained Coverage after Reconstructive Hip Surgery in Patients with Cerebral Palsy.” PMC. PMC ↗
“Fate of hips complicated by avascular necrosis of the femoral head following reconstructive surgery in nonambulatory patients with cerebral palsy.” PMC. PMC ↗

Medical disclaimer: This article is for informational purposes. Decisions about surgical timing should be made with specialists who have directly assessed your child’s specific situation.