多根髓内针及烤肉签针固定术治疗猫和小型犬复杂肱骨及股骨骨折。 机翻

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Introduction

Complex humeral and femoral fractures, including comminuted, segmental and long oblique configurations, are frequently encountered in cats and small‐breed dogs. These fractures present unique stabilisation challenges due to limited bone diameter, small fragment size, distal or metaphysial involvement and reduced implant purchase (Rausch et al. 2017; Trostle and Market 1996). Achieving adequate mechanical stability is particularly demanding in small patients, where conventional fixation systems may not always be optimally applicable.

Plate fixation is widely used for stabilisation of long bone fractures in small animals; however, its application may be limited in fractures with small distal or proximal fragments, narrow bone diameter or multifragmentary configurations. In such cases, obtaining sufficient screw purchase without further fragment damage may be difficult (Beck and Simpson 1999; Clarke and Carmichael 2006; Guerin et al. 1998; Piermattei et al. 2006). External skeletal fixation represents another alternative, but adequate stabilisation typically requires multiple pins in both proximal and distal fragments, which may be difficult when fragment length is limited or bone diameter is small. In addition, compared with the tibia or radius, application of bilateral external skeletal fixation constructs may be technically more challenging in the humerus and femur because of their proximity to the body and surrounding soft tissues (Aronsohn and Burk 2009; Kraus et al. 2003). As a result, achieving stable fixation in these fractures may be challenging with conventional methods.

Intramedullary pinning has been described for the stabilisation of long bone fractures in small animals and has been reported in various clinical studies. However, a single intramedullary pin may provide insufficient resistance to rotational and axial forces, particularly in unstable or comminuted fracture configurations (Rosa et al. 2019; Stiffler 2004). For this reason, intramedullary pinning alone is generally not recommended as the primary stabilisation method for many complex fractures. To improve construct stability, modifications such as the use of multiple intramedullary pins and additional fixation techniques have been described (Stiffler 2004). Nevertheless, published clinical reports evaluating the outcomes of these modified fixation strategies in complex humeral and femoral fractures of small patients remain limited.

The aim of this study was to evaluate clinical and radiographic outcomes of multiple intramedullary and skewer pin fixation in complex humeral and femoral fractures of cats and small‐breed dogs as an alternative fixation strategy in challenging fracture configurations.

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Materials and Methods

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Study Design and Animals

This retrospective study included 32 client‐owned animals (27 cats and 5 dogs) presented with complex humeral or femoral fractures between 2015 and 2025. All surgical procedures were performed by the corresponding author at six private veterinary clinics.

Clinical records and radiographs were reviewed to obtain data on signalment, fracture type and location, fixation method, postoperative alignment, healing time and functional outcomes. Cases were included if they involved cats or small‐breed dogs treated using multiple intramedullary pins, with or without additional stabilisation techniques, and had complete clinical records including preoperative and postoperative radiographs and follow‐up data.

All animals were treated as part of routine clinical care, and no experimental procedures were performed. In accordance with national regulations, formal ethical approval was not required. Informed owner consent was obtained for both treatment and the use of anonymised clinical data for publication.

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Surgical Technique

Anaesthesia was induced with xylazine HCl (2 mg/kg, IM; Alfazyne 2%, Alfasan International B.V., the Netherlands) followed by ketamine HCl (10 mg/kg, IM; Alfamine 10%, Alfasan International B.V.). Animals were intubated following induction, and anaesthesia was maintained with isoflurane (2%–2.5%; AErrane Volatile Solution, Baxter, Brazil) in oxygen. Perioperative monitoring included electrocardiography and pulse oximetry. The perioperative management protocols reflected routine clinical practice during the study period. A preoperative dose of ceftriaxone sodium (22 mg/kg, IV; Novosef, Zentiva, Czech Republic) was administered, followed by postoperative antibiotic therapy for 7 days. Analgesia was provided with meloxicam (0.1 mg/kg; Metacam, Boehringer Ingelheim, USA) administered preoperatively and continued for 4 days postoperatively. No additional nutritional or pharmacological supplements were routinely administered during the postoperative period.

Fractures were stabilised using multiple intramedullary Steinmann pins (1.2–1.5 mm), inserted either normograde or retrograde depending on fracture configuration. Pin diameter was selected primarily according to medullary canal size and fracture configuration rather than species alone. In general, 1.2 mm Steinmann pins were more commonly used in younger cats, whereas 1.5 mm pins were more commonly used in adult cats and small‐breed dogs. Additional stabilisation techniques, including skewer pinning or cerclage wiring, were applied in cases with oblique or highly comminuted fracture configurations. Skewer pin size was selected according to fragment size and the ability to achieve stabilisation without causing additional fragmentation.

In cases with oblique or highly comminuted fracture configurations, cerclage wires or absorbable sutures (USP 1 Polyglactin 910; Ethicon, Johnson & Johnson, USA) were used as adjunct techniques to support fragment positioning. The absorbable sutures were applied as simple supportive sutures around fracture fragments. In small animals, the limited soft tissue envelope may restrict the use of multiple cerclage wires due to potential soft tissue irritation and local discomfort. Therefore, absorbable sutures were preferred in some cases as a less invasive alternative to assist in maintaining fragment alignment. These sutures were not intended to provide primary mechanical stability but were used in combination with multiple intramedullary pins to support the anatomical alignment. This approach was considered sufficient during the early phase of biological fracture healing.

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Postoperative Management and Evaluation

Postoperative alignment was assessed based on radiographic evaluation of fragment apposition and overall limb alignment by the operating surgeon. Bone healing was evaluated based on radiographic evidence of callus formation and clinical limb use. All animals were recommended strict cage rest during the postoperative period. Functional outcome was assessed using a four‐grade walking scale (Fox et al. 1995), where Grade 1 represented excellent limb use with normal or near‐normal weight‐bearing and gait, Grade 2 indicated mild lameness with consistent limb use, Grade 3 represented moderate functional impairment with intermittent weight‐bearing and Grade 4 indicated poor functional outcome with severe lameness or non‐weight‐bearing.

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Statistical Analysis

Statistical analyses were performed using IBM SPSS Statistics version 29. Chi‐square tests were used for categorical variables, and one‐way ANOVA was used for continuous variables. Statistical significance was set at p < 0.05.

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Results

A total of 32 fractures (5 dogs and 27 cats) involving the humerus and femur were included in the study. Femoral fractures accounted for 27/32 cases (84%), whereas humeral fractures accounted for 5/32 cases (16%). Fractures included comminuted, segmental, long oblique, distal and intercondylar configurations involving both shaft and distal regions of the humerus and femur.

Postoperative evaluation demonstrated satisfactory anatomical alignment in the majority of cases. Alignment was classified as anatomical in 26 cases (81%), mildly angulated in 5 cases (15%) and severely angulated in 1 case (4%).

Radiographic union was achieved in the vast majority of cases (31/32, 97%). One case resulted in malunion, and one case had an unknown outcome due to lack of follow‐up.

Functional outcome assessment based on walking status revealed excellent results (Grade 1) in 24 cases (75%), good results (Grade 2) in 6 cases (19%) and poor outcome (Grade 4) in 1 case (3%). Outcome was unknown in one case due to lack of follow‐up. Overall, satisfactory functional outcome (Grade 1–2) was achieved in 94% of cases.

One femur case showed slight rotational malalignment but maintained good functional outcome without reoperation. One humerus fracture demonstrated fixation failure associated with early excessive activity.

No statistically significant association was identified between age and healing time or functional outcome (p > 0.05), although younger animals tended to show shorter healing times.

Fracture characteristics, healing times, and clinical outcomes are summarised in Tables 1 and 2.

Five representative cases are shown in Figures 1, 2, 3, 4, 5.

[图：A 5‐month‐old, 4 kg female cat (Case 2) with a comminuted distal femoral fracture involving the trochlea and femoral nec]

[图：An 8‐month‐old, 4.5 kg male cat (Case 4) with an oblique femoral shaft fracture. Preoperative (a) and postoperative radi]

[图：An 8‐month‐old, 4.5 kg female cat (Case 7) with a long oblique humeral shaft fracture. Preoperative (a) and postoperativ]

[图：A 10‐month‐old, 4 kg male cat (Case 9) with a highly comminuted femoral shaft fracture. Preoperative (a) and postoperati]

[图：A 1‐year‐old, 6 kg female cat (Case 25) with a segmental comminuted femoral shaft fracture. Preoperative radiographs (a–]

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Discussion

Comminuted fractures of the humerus and femur are commonly managed using bone plates or external fixators, which provide superior mechanical stability (Helfet et al. 2003; Piermattei et al. 2006; Ruedi et al. 2007). However, in cats and small‐breed dogs, the application of these implants may be limited due to insufficient fragment size for secure screw or pin placement (Beck and Simpson 1999; Clarke and Carmichael 2006; Guerin et al. 1998). In such cases, alternative fixation strategies may be considered (Guiot et al. 2019).

In the present study, multiple intramedullary pin fixation, with or without skewer pinning or cerclage support, was used to stabilise comminuted fractures. Although intramedullary pinning alone is generally considered biomechanically inferior to plate or external fixation (Rosa et al. 2019; Stiffler 2004), the results of this study demonstrate that it can still provide satisfactory functional outcomes under appropriate conditions.

A key finding of this study is that high rates of functional recovery were achieved despite the presence of mild malalignment or limited implant migration in some cases. This suggests that perfect anatomical reduction may not always be required, provided that adequate fragment contact and sufficient mechanical stability are achieved. Revision surgery was not considered necessary in these cases because radiographic healing progressed and clinically acceptable limb function was maintained. Under controlled postoperative conditions, including cage rest, this level of fixation appears to be sufficient to allow reliable bone healing and functional recovery (Claes et al. 2012; Perren 2002).

The success of this technique appears to depend on several factors. First, the use of multiple small‐diameter pins allows better adaptation to the medullary canal and may increase construct stability through multiple contact points and enhanced friction at the bone–implant interface (Hulse and Hymann 2003; Piermattei et al. 2006; Rudy 1974). Second, preservation of soft tissue attachments to bone fragments likely contributed to biological healing. Although intramedullary fixation may partially disrupt the medullary environment, experimental studies have reported that fracture healing and vascular response may still progress satisfactorily following intramedullary fixation techniques (Barron et al. 1977; Rand et al. 1981). Similarly, no apparent impairment of fracture healing associated with multiple intramedullary pin placement was observed in the present study, and satisfactory radiographic union was achieved in the majority of cases. Although mild implant migration was observed in some cases, these changes generally occurred after early callus formation had already developed and did not prevent satisfactory radiographic union or functional recovery. In addition, no clear association was observed between the number of fixation implants used and faster healing times. In some cases, absorbable sutures were used as an alternative to cerclage to reduce soft tissue irritation while maintaining fragment positioning in conjunction with multiple intramedullary pins. Third, controlled cage rest likely played a critical role in preventing excessive mechanical loading during the early healing phase. Although the animals were still able to bear weight on the operated limb within the cage environment, restriction of excessive activity such as jumping or uncontrolled movements was considered important because the fixation constructs provided relative rather than rigid stability.

Functional outcome assessment in the present study was based primarily on subjective clinical gait evaluation and owner observations, which represents a limitation of the retrospective study design.

Fixation failure was observed in a limited number of cases and was primarily associated with premature activity. This highlights the importance of postoperative management, particularly in small animals with high activity levels.

The humerus appeared more susceptible to fixation challenges compared to the femur, likely due to its anatomical shape and medullary canal configuration (Shipov et al. 2015). In distal humeral fractures, especially those involving condyles, additional fixation strategies such as transverse or skewer pinning may be necessary to improve stability.

Younger animals appeared to heal faster, which is consistent with established bone healing biology (Johnson 2018).

This study has several limitations. Its retrospective nature, variable follow‐up durations and reliance on subjective assessment of alignment may affect the generalizability of the findings. In addition, the absence of a control group treated with plate or external fixation limits direct biomechanical comparison. Successful application of these techniques may also depend on appropriate case selection and surgical experience.

Despite these limitations, the findings suggest that multiple intramedullary pin fixation can serve as a practical alternative fixation strategy for complex humeral and femoral fractures in cats and small‐breed dogs. Although plate osteosynthesis or external skeletal fixation may also be applicable in some cases, the present study demonstrates that this technique may still provide acceptable functional outcomes when applied carefully and supported by appropriate postoperative management.

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Conclusion

Multiple intramedullary pin fixation, with or without adjunct techniques such as skewer pinning or cerclage, can provide satisfactory functional outcomes in appropriately selected cases. This technique may represent a viable alternative in cases where conventional fixation methods are technically challenging.

Author Contributions

Yetkin Öztürk conceived and designed the study, performed all surgical procedures, collected and analysed the data, and prepared, wrote and revised the manuscript.

Funding

The author has nothing to report.

Ethics Statement

All procedures were performed as part of routine clinical care. In accordance with national regulations, formal ethical approval was not required. Informed owner consent was obtained for treatment and the use of anonymised data.

Conflicts of Interest

The author declares no conflicts of interest.