Subchondral lucencies of the proximal tibia in 17 horses

Abstract

Objective: To describe subchondral lucencies (SCL) in the equine proximal tibia, several treatment options, and clinical outcomes.Study design: Retrospective study.Animals: Seventeen horses with proximal tibial SCL. Methods: Medical record and radiograph review. Follow-up was obtained via examination and radiography when possible and by telephone and race records when required. The median duration of follow-up was 20 months (range, 0-48).Results: Proximal tibial SCL were associated with lameness in 14 of 17 horses.Subchondral lucencies were primary in 11 horses and secondary to an ipsilateral medial femoral condyle SCL in six horses. One foal with a primary SCL was euthanized because of osteomyelitis. Six horses ≤1 year old with primary SCL were managed with exercise restrictions only; SCL in three horses without lameness decreased in size, whereas three horses with lameness did not improve. One young horse treated with surgical debridement failed to improve and was euthanized. Lameness resolved in three horses with primary tibial SCL treated with screw fixation. Screw fixation of secondary SCL in five horses led to a reduction in SCL size and degree of lameness.Conclusion: Primary tibial SCL healed with rest in 3 non-lame young horses with small SCL, but was not successful in lame horses with larger SC. Radiographic size and associated lameness improved or resolved with screw fixation in primary and secondary proximal tibial SCL. Clinical significance: Primary tibial SCL that did not cause lameness healed with conservative management, but persistent primary and secondary tibial SCL required screw fixation to reduce lameness.

The failure mode of a mechanically loaded equine medial femoral condyle analog with a void and the impact of lag and neutral screw placement

“…The mechanical behavior of a specimen is determined by both geometry and material properties, 19 and clinical conclusions generated by this simplified MFC model should be made cautiously. However, the successful treatment of equine SCL in multiple locations after screw placement indicates a positive effect on bone healing 2,20,21 . Finite element modeling has predicted some aspects of bone mechanics 11,12 that are confirmed by this model and is a first step in understanding the practical mechanics of bone void failure and the impact of screw placement.…”

Subchondrale Knochenzysten – Von der Diagnostik zur Therapie

“…Ruhe und kontrollierte Bewegung , ggf. ergänzt durch Behandlung mit nicht-steroidalen Antiphlogistika , sind unspezifische Maßnahmen, die insbesondere bei jungen, lahmfreien Pferden mit kleinen SCL 34 , 35 als initiale Therapie eingesetzt werden. Die Erfolgsaussichten sind hierbei allerdings variabel 3 , 36 und Rezidive häufig 8 .…”

Compression generated by cortical screws in an artificial bone model of an equine medial femoral condylar cyst

“…Fully threaded screws used in lag fashion create compression when the tip end of the screw gains purchase in the far bone material and the screw head acts as a buttress 8,9 . The positive clinical results obtained after lag screw insertion in an MFC SCL 5 supports the clinical use of a lag screw to generate compressive force, but quantitative assessment of lag screw placement is surprisingly sparse in the literature 10 . For lag screws across MFC SCL, adequate MFC axial bone is necessary to achieve purchase of tip threads.…”

“…2 A study in 2015 reported that placement of a transcondylar lag screw as a treatment for equine medial femoral condyle (MFC) SCL resulted in similar or superior rates of lameness resolution and bone healing, 3 and other studies reported similar results in other locations. 4,5 The proposed mechanism is that the SCL directs strain around the void and screws create a compressive force across the SCL, redirecting strain and resulting in bone formation stimulus. 6 The technique was developed empirically, as direct measurement of bone strain in the MFC is impossible.…”

“…Traditional treatments of rest, anti‐inflammatory therapies and surgical debridement can reduce lameness, but radiographic bone healing is infrequent 2 . A study in 2015 reported that placement of a transcondylar lag screw as a treatment for equine medial femoral condyle (MFC) SCL resulted in similar or superior rates of lameness resolution and bone healing, 3 and other studies reported similar results in other locations 4,5 . The proposed mechanism is that the SCL directs strain around the void and screws create a compressive force across the SCL, redirecting strain and resulting in bone formation stimulus 6 .…”