Biomechanical comparison of two implants for the stabilization of incomplete ossification of the humeral condyle lesions in dogs

Clinical Assessment of a Lateral Epicondylar Anatomical Plate for the Stabilization of Humeral Condylar Fractures in Dogs

OBJECTIVE

 To report the use of a Lateral Epicondylar Anatomical Plate for the management of humeral condylar fractures (HCF) in dogs.

STUDY DESIGN

 Medical records of dogs with HCF stabilized using the Lateral Epicondylar Anatomical Plate at six UK veterinary referral centres between April 2018 and February 2021 were reviewed. Long-term follow-up (>6 months) was obtained via owner questionnaire, which incorporated the Liverpool Osteoarthritis in Dogs clinical metrology instrument.

RESULTS

 Sixty-two HCF were treated in 61 dogs (44 lateral condylar fractures [LCF] and 18 intracondylar (T/Y) fractures [ICF]). Fifty-one dogs were Spaniels or Spaniel crossbreeds. Intraoperative contouring of the plate was required for one dog-a French Bulldog. Postoperative complications occurred in 14/42 LCF and 6/18 ICF; overall there were 14 minor, 8 major, and 2 catastrophic complications. On final follow-up imaging, there was evidence of partial or complete osseous continuity of the condylar part of the fracture 32/53 HCF (24/39 LCF and 8/14 ICF) and lateral epicondylar part of the fracture in 53/53 HCF (39/39 LCF and 14/14 ICF). At final reexamination, 20/28 dogs with LCF and 5/13 dogs with ICF were not lame and the remaining dogs demonstrated mild lameness. According to the owner questionnaire, 17/17 dogs with LCF and 8/10 dogs with ICF returned to full limb use and median Liverpool Osteoarthritis in Dogs scores were 2/52 for LCF and 6.5/52 for ICF.

CONCLUSION

 The Lateral Epicondylar Anatomical Plate can be used successfully for the surgical stabilization of HCF in dogs.

Adjunctive fixation of the humeral epicondyle in a lateral condylar fracture model: Ex vivo comparison of pins and plates with a novel composite (AdhFix)

OBJECTIVE

To compare the biomechanical properties of using a novel composite construct (AdhFix) to an interfragmentary Kirschner wire or a reconstruction plate as adjunctive epicondylar stabilization in simulated lateral unicondylar humeral fractures.

STUDY DESIGN

Cadaveric biomechanical assessment.

SAMPLE POPULATION

Paired humeri harvested from skeletally mature dogs (14-41 kg), nine cadavers per group.

METHODS

Simulated lateral unicondylar humeral fractures were stabilized with a transcondylar 4.5 mm cortical screw placed in lag fashion. Adjunct fixations consisting of a novel composite incorporating 2.7 mm cortical screws on one side, and either a 2.7 mm reconstruction plate or a 1.6 mm Kirschner wire on the contralateral side, were tested within paired humeri. Repaired humeri were axially loaded to failure and construct stiffness, yield load, and ultimate load were obtained from the load-deformation curves.

RESULTS

In pairwise comparison, yield load was significantly higher for AdhFix group compared to the pin group, p = .016. No statistical significance was seen in the comparison between AdhFix group and the plate group, p = .25.

CONCLUSION

Adhfix was mechanically superior to K-wires, and comparable to plate fixation, for adjunctive fixation in a lateral humeral condylar model. Our results support further investigation of the novel composite for adjunct fracture fixation in lateral humeral condylar fractures.

CLINICAL SIGNIFICANCE

The novel composite tested may be a viable alternative for adjunct fixation of humeral condylar fractures, a technique that circumvents plate contouring.

Long-Term Outcome and Complications after Transcondylar Screw Placement for Canine Humeral Intracondylar Fissure

OBJECTIVE

 The aim of this study was to report postoperative complications and long-term outcomes following transcondylar screw placement for humeral intracondylar fissure (HIF).

STUDY DESIGN

 It was a retrospective single-centre case series. Medical records (2018-2022) were reviewed for dogs with HIF treated with transcondylar screw placement. Data collected included signalment, concurrent orthopaedic disease, partial or complete HIF, surgeon, surgical approach, surgical technique and implant type, transcondylar screw angulation, postoperative complications and outcomes. Long-term outcome was assessed with owner questionnaire, orthopaedic examination and follow-up radiography. Statistical analysis was performed to identify risk factors predisposing to a complication or a poor outcome.

RESULTS

 Forty-seven dogs (57 elbows) met the inclusion criteria; long-term follow-up was available in 41 dogs (50 elbows). Minor and major medical complications were noted in seven and three elbows respectively. The total complication rate was 17.5%. Increasing age was significantly associated with a reduced risk of postoperative complications (p = 0.0051). No other risk factors were identified. A postoperative complication was not associated with a less than full outcome (p = 0.5698).

CONCLUSION

 Transcondylar screw placement for HIF is associated with a low complication rate and good outcome.

Biomechanical comparison of humeral condyles with experimental intracondylar fissures immobilized with a transcondylar positional or a lag screw: An ex-vivo study in dogs

OBJECTIVE

To compare the axial biomechanical properties of intracondylar humeral osteotomies fixed with 4.5 mm transcondylar positional or cortical lag screws.

STUDY DESIGN

Ex vivo study.

SAMPLE POPULATION

Paired humeri from 21 canine cadavers.

MATERIALS AND METHODS

An intracondylar osteotomy was created on each humerus to mimic an intracondylar fissure. Paired humeri were randomly assigned to fixation with a positional or a lag screw. All specimens were radiographed postinstrumentation to document proper screw placement. Axial load was applied to the distal articular surface of the trochlea at a rate of 1 mm/s until a 40% decrease in load was measured. Specimens were assessed for mode of failure with visual inspection and radiographs.

RESULTS

Stiffness (1236.7 ± 181 N/mm vs. 1050.8 ± 265 N/mm), yield load (3284.3 ± 1703 N vs. 2071.1 ± 740 N), and maximum load (7378.0 ± 1288 vs. 5793.7 ± 2373 N) were greater in constructs fixed with a positional rather than a lag screw (p = .0008, .044, and .040, respectively).

CONCLUSION

In our model, mechanical properties were improved when the transcondylar osteotomy was stabilized with a 4.5 mm positional screw rather than a lag screw.

CLINICAL SIGNIFICANCE

This ex vivo study suggests that a transcondylar lag screw and positional screw are not biomechanically equal. Additional in vivo studies are need to help with clinical decision making when prophylactically treating HIF.

Accuracy of medial-to-lateral transcondylar screw placement using an aiming device and preoperative computer tomography planning for the treatment of humeral intracondylar fissure

OBJECTIVE

To determine the accuracy of transcondylar screws placed from medial-to-lateral using preoperative planning on computed tomography (CT) and an aiming device in elbows with humeral intracondylar fissures (HIFs).

STUDY DESIGN

Retrospective case series.

ANIMALS

Twenty-five client-owned dogs with HIF.

METHODS

A 4.5-mm transcondylar screw was placed in 34 elbows with HIF. humeral condylar diameter (HCD) was measured at the humeral condylar isthmus on CT. Entry and exit points were planned at 0.3 × HCD cranial and 0.2 × HCD distal to the medial epicondyle and 0.3 × HCD cranial and 0.3 × HCD distal to the lateral epicondyle. An aiming device was used to guide drilling from the medial entry point to the lateral exit point. The difference between planned and actual screw entry and exit points, and the angular deviation of the actual screw axis from the planned screw axis, was assessed on the postoperative CT scans.

RESULTS

Thirty-three out of 34 screws were completely within the humeral condyle. Thirteen out of 34 screws were placed less than 2 mm from planned entry and exit points in both the transverse and the frontal plane. The axis of the screw deviated by a mean of 3.2° (transverse plane) and 3.5° (frontal plane) from the planned axis.

CONCLUSION

Humeral transcondylar screws placed with the technique tested here were entirely within the humeral condyle in 33 out of 34 elbows.

CLINICAL SIGNIFICANCE

Use of CT planning and an aiming device allows accurate placement of transcondylar screws from medial-to-lateral in dogs with HIF.

Humeral Intracondylar Fissure in Dogs

Humeral intracondylar fissure (HIF) was first described as incomplete ossification of the humeral condyle. It is now known that the fissure is a stress fracture in some dogs. The descriptive term HIF is therefore preferred. In young dogs an incomplete ossification cause may still be valid. Symptomatic HIF is treated surgically with a transcondylar implant. The aim is to alleviate lameness and avoid condylar fracture. Choosing an appropriate surgical approach and implant can reduce complications. HIF is not always symptomatic and, in these cases, surgical management is more controversial, because a minority of such cases become lame or fracture.

Effect of Induced Incomplete Ossification of the Humeral Condyle on Ex Vivo Humeral Condylar Biomechanics

OBJECTIVE

 The aim of this study was to investigate the effects of an induced incomplete ossification of the humeral condyle (IOHC) lesion on ex vivo canine humeral condylar biomechanics.

STUDY DESIGN

 Nine paired cadaveric elbows were collected from mature dogs weighing between 20 and 25 kg. Left and right limbs were randomized to IOHC or normal groups. Limbs were prepared for mechanical testing; ligaments were preserved and an IOHC lesion was created. Elbows were potted, positioned into a biomaterials testing system at an angle of 135 degrees and axially loaded to failure at a rate of 30 mm/minute.

RESULTS

 Induced IOHC lesions reduced peak load (p = 0.02) when compared with an intact humerus. There was no difference between stiffness (p = 0.36) of intact humeri or humeri with an induced IOHC lesion. An induced IOHC lesion increased (p = 0.012) the probability of intracondylar fracture under load.

CONCLUSION

 Cadaveric humeri are weakened by the creation of an intracondylar osteotomy and fractures secondary to induced IOHC are similar to spontaneous humeral condylar fractures. These findings support the hypothesis that naturally occurring IOHC weakens the humeral condyle and may predispose to humeral condylar fracture.