# Radiographic Assessment of Fracture Healing in Dogs and Cats


## Key Takeaways

- Cortical continuity, assessed on orthogonal radiographic views, is the most critical radiographic predictor of fracture strength, correlating strongly with torsional strength; callus volume is a poor predictor and should not be solely relied upon for assessing healing.
- Radiographic union is typically achieved by 8-12 weeks in adult dogs for diaphyseal fractures, with cats often healing faster; delayed union is indicated by a lack of radiographic progression between studies spaced 4-6 weeks apart.
- The Radiographic Union Score provides a standardized, semiquantitative method for assessing fracture healing progression by evaluating cortical bridging and remodeling across four cortices, with a score of 9 or greater often indicating clinical union.
- Plain radiographs cannot accurately predict the mechanical strength of a healing fracture, necessitating integration of radiographic findings with clinical assessment (palpation, weight-bearing status) to guide decisions on activity restriction and fixation management.
- Implant integrity must be meticulously evaluated for signs of loosening, bending, or breakage, as these complications can compromise stability, impede healing, and precede clinical failure, often manifesting as a lack of radiographic progression.
- Cats tend to form less periosteal callus than dogs, and their healing timelines can be faster, requiring adjusted interpretation of radiographic findings, with a greater emphasis placed on cortical bridging and fracture line obliteration.

---

Radiography remains the most widely used imaging method for monitoring fracture repair in small animal practice. This article provides a structured approach to interpreting follow-up radiographs in dogs and cats, with emphasis on expected timelines, criteria for union, and the limitations of plain radiographs in predicting mechanical strength. It is written for practicing veterinarians who manage fracture patients and need a defensible framework for clinical decision-making.

The central clinical questions are straightforward: Is this fracture healing at an acceptable rate? Is union present or imminent? Should fixation be revised, or should activity restrictions be relaxed? Radiographs provide the primary evidence, but their interpretation requires an understanding of the biological stages of repair, the influence of fixation stability, and the statistical relationship between radiographic appearance and actual bone strength. This article addresses each of these areas and introduces the scoring systems used to standardize assessment.

## At a Glance

| Parameter | Clinical Relevance | Key Points |
|---|---|---|
| Radiographic union definition | Determines when fixation can be removed and activity increased | Cortical continuity is the strongest radiographic predictor of strength |
| Expected healing time | Identifies delayed union | Diaphyseal fractures in dogs typically show radiographic union by 8 to 12 weeks, cats may heal faster |
| Callus appearance | Reflects fixation stability | Large periosteal callus suggests motion, minimal callus suggests rigid fixation |
| Scoring systems | Standardize assessment | The Radiographic Union Score provides a structured, repeatable evaluation |
| Radiographic limitations | Prevents overconfidence | Plain radiographs cannot accurately predict fracture strength |
| Serial comparison | Essential for trend detection | A single radiograph is less informative than a sequence |
| Implant integrity | Detects fixation failure | Screw loosening, plate bending, or pin migration alter the healing trajectory |

## Biology of Fracture Repair Relevant to Radiographic Interpretation

Fracture healing proceeds through overlapping phases: inflammation, soft callus formation, hard callus formation, and remodeling. The radiographic appearance at any time point reflects the dominant phase and the mechanical environment. Under stable fixation, healing may occur with minimal periosteal callus, a pattern termed primary or direct bone healing. Under less rigid conditions, abundant periosteal callus forms, and the fracture heals through an indirect or secondary pathway. Both patterns are normal, but they produce very different radiographic appearances, and the clinician must interpret each in the context of the fixation method used.

Fixation stiffness directly influences the healing mechanism. Experimental work in canine tibial osteotomies has shown that more rigid external fixation produces early clinical union with less periosteal callus, while less rigid fixation is associated with significantly increased callus formation at later time points. The same study found that structural strength of the healed bone was not significantly different between rigid and flexible fixation groups, although the less rigid group required a longer period for repair and remodeling. This means the radiologist should not interpret a large callus as a sign of failure, nor a small callus as a sign of inadequate healing, without knowing the fixation construct.

## Radiographic Parameters of Healing

### Cortical Continuity

Cortical continuity is the single most important radiographic feature. In an experimental study of healing rabbit tibial osteotomies, cortical continuity showed the strongest correlation with torsional strength, with a correlation coefficient of 0.80. Callus area was the least predictive parameter, and fracture displacement, callus thickness, and callus diameter all showed negative correlations with strength. These findings support a simple clinical rule: assess bridging of the cortices on orthogonal views before considering the fracture healed, and do not rely on callus size as evidence of strength.

### Callus Characteriztics

Callus should be evaluated for volume, density, and bridging. Early callus is soft and poorly mineralized, appearing as a faint, amorphous opacity. Progressive mineralization produces a more defined trabecular pattern. Bridging callus that connects both cortices on at least two orthogonal projections is a favorable sign. However, the experimental data caution against equating callus volume with mechanical integrity. A large, poorly mineralized callus may represent instability and delayed maturation instead of robust healing.

### Fracture Gap and Alignment

The width of the fracture gap should decrease over time. Persistent widening suggests resorption, infection, or excessive motion. Angular deformity, translation, or rotational malalignment should be measured and compared with previous studies. Progressive displacement indicates fixation failure and warrants immediate reassessment of the implant construct.

### Implant Integrity

Radiographs must be scrutinized for implant complications. Screw loosening appears as a radiolucent halo around the screw shaft or as screw migration. Plate bending or breakage, pin bending, and wire breakage all indicate that the implant is bearing more load than intended. These findings often precede clinical failure and may explain a lack of radiographic progression.

## The Radiographic Union Score

The Radiographic Union Score is a semiquantitative tool adapted from human orthopedics for use in small animals. It assigns points for cortical bridging, callus presence, and remodeling on each of four cortices visible on orthogonal radiographs. The total score ranges from 0 to 16, with higher scores indicating more advanced healing. A score of 10 or greater is often used as a threshold for considering the fracture clinically united, although the exact cutoff varies by anatomic location and fixation type.

The score provides two practical benefits. First, it forces a systematic evaluation of each cortex instead of a global impression. Second, it allows serial scores to be plotted over time, making delayed healing more obvious. The score does not replace clinical judgment, but it reduces interobserver variability and provides a common language for communication with colleagues and clients.

## Limitations of Radiographic Assessment

Plain radiographs provide structural information but cannot measure the material properties of the healing bone. The experimental literature is explicit on this point: even under controlled laboratory conditions, information from plain radiographs is not sufficient to accurately predict the strength of a healing fracture. This limitation has practical consequences. A fracture that appears radiographically healed may still be vulnerable to refracture under high loads, particularly if remodeling is incomplete. Conversely, a fracture with a modest callus may have adequate strength if cortical continuity is present.

The clinician should therefore use radiographs as one component of a broader assessment that includes palpation, weight-bearing status, and time since surgery. When radiographic findings and clinical findings conflict, the more conservative interpretation should guide recommendations. Advanced imaging such as computed tomography provides superior assessment of bridging and cross-sectional area, but its availability and cost limit routine use in general practice.

## Standard Radiographic Monitoring Protocol

Fracture healing is assessed radiographically at defined intervals, but the timing of those intervals depends on the patient, the fracture configuration, and the stability of the fixation. For most diaphyseal fractures in dogs and cats, initial postoperative radiographs are obtained immediately after surgery to document reduction and implant position. Subsequent radiographs are typically scheduled at 2 to 4 week intervals for the first 8 weeks, then at 4 to 6 week intervals until union is confirmed. Cats generally heal faster than dogs, and juvenile animals heal substantially faster than adults. A 6 month old cat with a simple femoral fracture may show radiographic union at 4 to 6 weeks, whereas a 9 year old large breed dog with a comminuted tibial fracture may require 12 to 20 weeks or longer.

The decision to obtain follow-up radiographs should be driven by clinical examination findings as much as by the calendar. Lameness that persists or worsens beyond the expected postoperative period, focal swelling or warmth at the fracture site, crepitus, or a sudden change in weight-bearing status all warrant earlier radiographic evaluation. Conversely, a patient that is bearing weight comfortably and shows no palpable instability may not need radiographs at every scheduled interval. The clinician should balance the value of serial imaging against the cost, the need for sedation or anesthesia, and the radiation exposure to the patient and staff. Professional guidance on radiation safety and imaging protocols is available through the [American College of Veterinary Radiology resources](https://acvr.org/).

A standard radiographic study for fracture monitoring includes two orthogonal views of the affected bone, centered on the fracture site. The limb should be positioned consistently between studies so that comparisons of callus size, gap width, and alignment are meaningful. Magnification should be controlled by keeping the bone close to the cassette or detector and using a consistent source to image distance. Oblique views may be added when the fracture is complex, when the gap is obscured by implant artifact, or when cortical continuity on one side cannot be assessed on the orthogonal projections. Stress views are rarely indicated and should be interpreted with caution, as they can overestimate instability in the presence of compliant soft tissues.

## Radiographic Union Scoring in Practice

The radiographic union score provides a structured method for documenting progression toward union and for communicating that progression to other clinicians. The score is applied to each cortex on each orthogonal view, and the individual scores are summed to produce a total. A commonly used system assigns a score of 0 to 3 for each cortex based on the degree of bridging. A score of 0 indicates no visible callus or bridging. A score of 1 indicates callus present but no bridging. A score of 2 indicates bridging callus that is still incomplete or less dense than normal cortical bone. A score of 3 indicates complete bridging with remodeling, where the callus is continuous with the cortex and the fracture line is no longer visible.

The table below presents a radiographic union scoring framework suitable for clinical use in dogs and cats.

| Score | Cortical bridging | Remodeling | Radiographic appearance |
|-------|-------------------|------------|-------------------------|
| 0 | None | None | No callus or minimal periosteal reaction, fracture line clearly visible |
| 1 | None | None | Callus present but does not cross the fracture gap |
| 2 | Partial | Early | Callus bridges the gap but is less dense than cortex, fracture line partially visible |
| 3 | Complete | Present | Callus is continuous with cortex, fracture line no longer visible, medullary canal may be re-establishing |

Each cortex is scored independently on each view. For a femoral fracture, the medial and lateral cortices are scored on the craniocaudal view, and the cranial and caudal cortices are scored on the lateral view. The four scores are summed to give a total out of 12. A total of 9 or higher with no individual cortex scoring below 2 is generally considered consistent with radiographic union, although this threshold has not been validated in dogs and cats to the same degree as in human orthopedics. The score is most useful as a serial measure: a rising score over consecutive studies confirms progression, while a static or falling score raises concern for delayed union or implant failure.

The correlation between radiographic appearance and mechanical strength of the healing fracture is imperfect. Experimental work in rabbit tibial osteotomies found that cortical continuity was the best single radiographic predictor of torsional strength, with a correlation coefficient of 0.80, while callus area was a poor predictor at 0.17 [correlation of radiographic healing with fracture strength](https://pubmed.ncbi.nlm.nih.gov/3998898/). This finding supports the emphasis on cortical bridging instead of callus volume when scoring healing. A large, exuberant callus may look reassuring but does not necessarily indicate that the fracture is strong enough for full weight-bearing. Conversely, a fracture with minimal visible callus may still be mechanically sound if cortical continuity is present.

## Decision Points and What Changes the Decision

The radiographic findings at each monitoring interval feed directly into clinical decisions about activity restriction, fixation changes, and the need for additional intervention.

**Activity restriction.** When the radiographic union score is 6 or lower, or when cortical bridging is absent on any cortex, the fracture is considered mechanically fragile. Strict activity restriction, including cage rest and leash walks only, should continue. When the score reaches 9 or higher and at least three cortices show complete bridging, a gradual return to normal activity can begin. The rate of progression should be guided by the patient's comfort and by the presence or absence of lameness on increasing exercise.

**Fixation changes.** External fixators are often destabilized or removed in stages as healing progresses. Radiographic evidence of bridging callus on two or more cortices supports converting a rigid fixator to a more flexible configuration, such as removing connecting bars or converting to a tied-in configuration. Complete removal of the fixator is typically delayed until the union score is 9 or higher. The stiffness of the fixation influences the healing pathway: experimental work in canine tibial osteotomies showed that less rigid external fixation produced significantly more periosteal callus at 90 and 120 days, but also a longer overall remodeling period [external fixation stiffness and osteotomy healing](https://pubmed.ncbi.nlm.nih.gov/6490701/). A clinician managing a fracture under a less rigid fixator should therefore expect a longer time to radiographic remodeling and should not interpret persistent callus as a sign of failure.

**Delayed union and nonunion.** A fracture that shows no radiographic progression between two consecutive studies taken 4 to 6 weeks apart is classified as a delayed union. If the fracture gap remains visible and no bridging callus has formed by 4 to 6 months in an adult dog, the diagnosis of nonunion should be considered. Radiographic features of nonunion include a persistent radiolucent gap, sclerotic bone ends, and rounding of the fracture margins. At this point, the clinician must decide whether to continue conservative management, revise the fixation, or pursue biologic augmentation. The evidence for biologic adjuncts in nonunion management comes largely from human studies, including a randomized trial showing that recombinant human osteogenic protein-1 (BMP-7) produced clinical and radiographic results comparable to autogenous bone graft in tibial nonunions [osteogenic protein-1 in tibial nonunion treatment](https://pubmed.ncbi.nlm.nih.gov/11314793/). These findings are not directly transferable to dogs and cats, but they support the rationale for considering bone grafting or biologic stimulation in cases where mechanical stability is adequate yet healing has stalled.

## Documentation and Communication

Radiographic findings should be documented in the medical record using a consistent format. The record should include the date of the study, the views obtained, the radiographic union score for each cortex, the total score, and a written description of callus quality, gap width, alignment, and implant integrity. Serial scores should be plotted or tabulated so that trends are immediately visible. This documentation serves multiple purposes: it supports clinical decision-making at the next recheck, it provides a legal record of the monitoring process, and it facilitates communication with referral surgeons or emergency clinicians who may see the patient between scheduled visits.

The written description should use standard terminology. Terms such as "early periosteal callus," "bridging callus," "incomplete cortical bridging," and "remodeling" should be used consistently. Ambiguous phrases such as "healing well" or "good callus formation" should be avoided in favor of specific descriptors that another clinician could reproduce from the images alone. When the interpreting clinician is not the surgeon who placed the implants, the report should note any implant-related concerns, including screw loosening, plate bending or breakage, pin tract lysis, or migration of pins or wires.

## Species and Patient Considerations

Cats differ from dogs in several ways that affect radiographic monitoring. Feline bone heals faster, with radiographic union often achieved by 6 to 8 weeks in simple fractures. Cats also tend to form less periosteal callus than dogs, so the absence of a large callus should not be interpreted as delayed healing. The radiographic union score thresholds should be adjusted accordingly: a cat with a score of 8 at 6 weeks may be clinically ready for normal activity, whereas a dog with the same score at 10 weeks may require continued restriction.

Body condition affects radiographic interpretation. Obese patients produce more soft tissue opacity that can obscure the fracture site, and positioning is more difficult. The radiographic beam may need to be centered more carefully, and oblique views may be required more often. Skeletal immaturity introduces the additional challenge of distinguishing normal growth plate appearance from fracture lines, particularly in the distal femur and proximal tibia. Comparison views of the contralateral limb can be helpful in juvenile patients.

The available imaging equipment also changes the approach. Digital radiography allows windowing and magnification that can improve assessment of fine callus detail, but it does not change the fundamental limitation that plain radiographs cannot accurately predict the mechanical strength of a healing fracture [radiographic analysis correlation with fracture strength](https://pubmed.ncbi.nlm.nih.gov/3998898/). Advanced imaging such as CT is superior for assessing cortical bridging in complex fractures, particularly where implant artifact obscures the radiographic view, but CT is not available in all practices and requires general anesthesia in most patients. The clinician should use the modality that answers the specific clinical question with the least risk and cost to the patient.

## Recognized Complications and Early Detection

Delayed union, nonunion, and malunion remain the principal radiographic complications of fracture repair. A delayed union is diagnosed when serial radiographs show progressive but slower than expected healing. A nonunion is declared when healing has arrested, with no radiographic change across two examinations spaced four to eight weeks apart. The radiographic hallmarks of nonunion include a persistent radiolucent gap, sclerotic bone ends, and rounding or capping of the fracture fragments. Hypertrophic nonunions show abundant but nonbridging callus, whereas atrophic nonunions show minimal or absent callus formation. The distinction matters because hypertrophic nonunions usually reflect inadequate stability, while atrophic nonunions suggest compromised biology, infection, or poor vascularity.

Early detection depends on disciplined serial radiography. A single postoperative radiograph establishes the baseline reduction, implant position, and fracture gap. The next study at four to six weeks should show early periosteal reaction and progressive gap filling. If the gap remains unchanged and the fracture margins appear sharper instead of softer, healing has stalled. Cortical continuity is the strongest single radiographic predictor of mechanical strength, so its absence at the expected time point should trigger reassessment instead of continued observation [Panjabi and colleagues' correlation of radiographic parameters with fracture strength](https://pubmed.ncbi.nlm.nih.gov/3998898/).

Implant failure is often the first objective sign of a biomechanical problem. Screw loosening appears as a radiolucent halo around the screw shaft or as migration of the screw within the bone. Plate breakage or bending is usually obvious, but fatigue fractures of plates can be subtle and may require oblique projections to visualize. Pin tract lysis around external fixator pins indicates loosening or infection and is more common with less rigid constructs, which also show increased periosteal callus formation as the healing mechanism shifts toward external bridging [Wu and colleagues' comparison of osteotomy healing under external fixation devices](https://pubmed.ncbi.nlm.nih.gov/6490701/).

Osteomyelitis complicates radiographic interpretation. Bone lysis, periosteal new bone formation that is irregular or palisading, and soft tissue swelling beyond the expected postoperative envelope all raise suspicion. Sequestra appear as dense, separate bone fragments within a lucent cavity. Radiographic changes of infection lag behind clinical signs, so persistent lameness, draining tracts, or fever warrant aggressive investigation even when radiographs appear reassuring.

## Common Interpretation Errors

The most frequent error is equating callus volume with healing. Large callus can accompany a nonunion, and small callus can accompany a solid union under rigid fixation. Callus area correlates poorly with fracture strength, and displacement, callus thickness, and callus diameter can even show negative correlations with strength [statistical analysis of radiographic healing parameters](https://pubmed.ncbi.nlm.nih.gov/3998898/). The clinician should evaluate bridging across cortices, not the bulk of new bone.

A second error is reading a single radiograph in isolation. Healing is a temporal process, and the only reliable way to distinguish delayed from arrested healing is comparison with prior studies. A third error is overinterpreting the significance of the radiographic appearance for weight-bearing capacity. Plain radiographs cannot accurately predict the strength of a healing fracture, even under controlled laboratory conditions, so clinical assessment of weight-bearing must be integrated with imaging findings [Panjabi and colleagues' experimental osteotomy analysis](https://pubmed.ncbi.nlm.nih.gov/3998898/).

A fourth error is failing to obtain orthogonal views. A bridging callus visible on one projection may be absent on the perpendicular view, and the true gap is often larger than it appears on a single radiograph. Oblique views are underused and can reveal incomplete bridging or implant complications hidden by superimposition.

| Observation | Likely cause | Discriminating check |
|---|---|---|
| Progressive lucency around screw | Screw loosening or early infection | Compare prior films, assess clinical lameness, consider repeat radiograph in 2 weeks |
| Large callus, persistent gap | Hypertrophic nonunion from instability | Assess implant integrity, check fracture gap on orthogonal views |
| Minimal callus, sharp margins | Atrophic nonunion or compromised biology | Review drug history, including opioid use, investigate infection |
| Irregular periosteal reaction with lysis | Osteomyelitis | Look for sequestra, correlate with fever, drainage, leukocytosis |
| Sudden increase in callus after stable period | Implant fatigue or loosening | Obtain oblique projections, scrutinise plate and screw interfaces |

## Evidence Limitations and Divergent Expert Opinion

The evidence base for radiographic fracture assessment in small animals is thin. Most quantitative correlations between radiographic appearance and mechanical strength derive from experimental osteotomies in rabbits, and those data show that plain radiographs are insufficient to predict strength accurately [correlation of radiographic analysis with fracture strength](https://pubmed.ncbi.nlm.nih.gov/3998898/). Extrapolation to dogs and cats, to different bones, and to different fixation methods requires caution.

Expert opinion diverges on several points. The optimal frequency of radiographic monitoring is not standardized, with recommendations ranging from every two weeks to every six weeks depending on the fracture and the clinician's preference. The definition of radiographic union also varies, with some authorities accepting a single bridged cortex and others requiring circumferential bridging. The role of advanced imaging, particularly CT, is expanding, but its superiority over serial radiography for clinical decision-making has not been established in veterinary patients.

Systemic factors that delay healing are increasingly recognized. Postoperative opioid administration has been shown to reduce callus strength and delay callus maturation in a rat femoral osteotomy model, raising questions about routine analgesic protocols in fracture patients [postoperative opioid effects on bone healing in an animal model](https://pubmed.ncbi.nlm.nih.gov/23955193/). The clinical relevance in dogs and cats is uncertain, but the finding supports minimizing opioid exposure where alternative analgesia is adequate.

## Referral and Escalation Criteria

Referral to a veterinary orthopedic specialist is warranted when a nonunion is confirmed, when implant failure compromises stability, when infection is suspected or confirmed, or when healing has not progressed across two consecutive monitoring intervals. Early referral is preferable to prolonged conservative observation, because delayed intervention reduces the chance of successful salvage.

Specialist consultation is also appropriate when the clinician is uncertain whether the radiographic appearance represents normal variation or pathology. The American College of Veterinary Radiology maintains resources on imaging standards and can direct practitioners to board-certified radiologists for second opinions [ACVR professional resources](https://acvr.org/). Laboratory involvement is indicated when osteomyelitis is suspected, with aerobic and anaerobic culture of deep tissue samples or of the implant surface, not of draining tracts alone.

Regulatory reporting obligations vary by jurisdiction. Suspicion of non-accidental injury, particularly in animals with multiple fractures at different healing stages or fractures inconsistent with the reported history, may trigger mandatory reporting under local animal welfare statutes. The World Organization for Animal Health publishes international standards for animal welfare that inform such reporting frameworks [WOAH terrestrial animal health standards](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/). Clinicians should know the requirements of their own jurisdiction and document the radiographic findings that support their concern.

## Frequently Asked Questions

### How should I monitor fracture healing when advanced imaging is unavailable?

Standard orthogonal radiography remains the primary monitoring tool in most practice settings. The [American College of Veterinary Radiology resources](https://acvr.org/) emphasize that properly positioned, well-exposed radiographs provide adequate information for serial assessment in the majority of cases. When digital radiography is unavailable, use a consistent technique with a fixed exposure chart and ensure identical positioning between studies. Document the radiographic union score at each visit and compare against the previous study instead of relying on memory. If radiographs are technically inadequate, repeat them before making clinical decisions. Cross-sectional imaging adds value for complex or equivocal cases but is not required for routine monitoring of uncomplicated fractures.

### What is the minimum frequency for follow-up radiographs in a typical fracture?

Most protocols recommend radiographs at four to six week intervals until cortical continuity is visible across at least three cortices. The [MSD Veterinary Manual](https://www.msdvetmanual.com/) provides general guidance on fracture management timelines, though specific intervals depend on patient age, fracture location, and fixation method. Immature animals may show radiographic union within four to six weeks, whereas adult large-breed dogs often require twelve to sixteen weeks. If the clinical examination suggests premature implant failure or progressive lameness, obtain radiographs earlier than scheduled. After radiographic union is confirmed, a single follow-up study at eight to twelve weeks post-union helps document remodelling and detect late complications such as implant loosening or stress protection.

### How do I explain delayed radiographic healing to an owner without causing unnecessary alarm?

Frame the discussion around the radiographic findings and the planned response. Explain that the fracture is healing more slowly than expected but that this does not necessarily indicate failure. Describe the specific parameters observed, such as limited callus formation or persistent fracture line, and relate these to the clinical picture. The [AVMA practice resources](https://www.avma.org/resources-tools) offer general guidance on client communication in complex medical situations. Offer a concrete plan: repeat radiographs in two to four weeks, adjust activity restrictions, and consider additional diagnostics if healing remains static. Avoid definitive predictions about outcome until serial studies establish a trend. This approach maintains owner confidence while preserving clinical honesty.

### Does fracture healing differ between cats and dogs radiographically?

Cats generally form less periosteal callus than dogs, particularly in the humerus and femur. A healing feline fracture may show subtle endosteal bridging with minimal external callus, which can be mistaken for delayed union if the observer expects a canine pattern. Conversely, cats are prone to delayed unions and nonunions in the radius and ulna, especially with comminuted fractures or compromised blood supply. The [MSD Veterinary Manual](https://www.msdvetmanual.com/) notes species-specific differences in bone biology and healing responses. When assessing feline radiographs, place greater weight on cortical continuity and fracture line obliteration than on callus volume. If the fracture gap remains visible beyond twelve weeks in an adult cat, pursue additional imaging or referral.

### What should I record in the medical record for each radiographic assessment?

Record the date, radiographic projections obtained, and the radiographic union score with its individual component values. Describe the number of cortices bridged, callus characteriztics including volume and density, fracture gap width, and any change in alignment. Document implant position and note any signs of loosening, bending, or breakage. The [American College of Veterinary Radiology resources](https://acvr.org/) support standardized reporting to improve diagnostic consistency. Include a comparison with the previous study, stating whether findings are improved, static, or worse. Record the clinical assessment alongside the radiographic findings, since function and imaging do not always correlate. This documentation supports clinical decisions, client communication, and medicolegal defensibility.

### When should I refer a case with delayed radiographic healing?

Refer when radiographic union has not progressed across two consecutive studies four weeks apart, when the radiographic union score is static or declining, or when implant failure compromises stability. Referral is also appropriate when the fracture involves the articular surface with persistent step-off, when infection is suspected, or when the radiographic appearance suggests a nonunion with sclerotic margins and a persistent gap. The [WOAH terrestrial animal health standards](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) address broader professional obligations regarding animal welfare and timely intervention. Before referral, obtain current radiographs and a complete history including all previous imaging, implant details, and any medications administered. Opioid analgesia has been associated with delayed callus maturation in experimental models, so document the analgesic history when escalating care.

## Related Clinical & Scientific Guides

* [MRI Monitoring of Brain Tumor Response to Therapy in Dogs](/knowledge/veterinary-medicine/diagnostic-imaging/mri-monitoring-brain-tumor-response-therapy-dogs)
* [Ultrasound-Guided Drainage of Abscesses in Small Animals](/knowledge/veterinary-medicine/diagnostic-imaging/ultrasound-guided-drainage-abscesses-small-animals)
* [Radiographic Monitoring of Total Hip Replacement in Dogs](/knowledge/veterinary-medicine/diagnostic-imaging/radiographic-monitoring-total-hip-replacement-dogs)


## References and Further Reading

- [Acceleration of fresh fracture repair using the sonic accelerated fracture healing system (SAFHS): a review.](https://pubmed.ncbi.nlm.nih.gov/10652965/). 2000.
- [Osteogenic protein-1 (bone morphogenetic protein-7) in the treatment of tibial nonunions.](https://pubmed.ncbi.nlm.nih.gov/11314793/). 2001.
- [Correlations of radiographic analysis of healing fractures with strength: a statistical analysis of experimental osteotomies.](https://pubmed.ncbi.nlm.nih.gov/3998898/). 1985.
- [In situ bone tissue engineering via ultrasound-mediated gene delivery to endogenous progenitor cells in mini-pigs.](https://pubmed.ncbi.nlm.nih.gov/28515335/). 2017.
- [Comparison of osteotomy healing under external fixation devices with different stiffness characteriztics.](https://pubmed.ncbi.nlm.nih.gov/6490701/). 1984.
- [Postoperative opioid administration inhibits bone healing in an animal model.](https://pubmed.ncbi.nlm.nih.gov/23955193/). 2013.
- [American College of Veterinary Radiology Resources](https://acvr.org/). American College of Veterinary Radiology.
- [MSD Veterinary Manual, Professional Edition](https://www.msdvetmanual.com/). MSD Veterinary Manual.
- [American Veterinary Medical Association Practice Resources](https://www.avma.org/resources-tools). American Veterinary Medical Association.

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> This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.