Treatment Comparison for Medial Femoral Condyle Subchondral Cystic Lesions and Prognosis in Yearling Thoroughbred Racehorse Prospects

Subchondral cystic lesions (SCL) in the medial femoral condyle are a usual finding in Thoroughbred survey and auction repository radiographs. Several treatments with different outcomes have been studied over the years to improve soundness and racing prognosis. Our objective was to report the racing prognosis in Thoroughbred yearlings intended for racing that were diagnosed with SCL in the medial femoral condyle and were treated using four current and different techniques: intralesional injection of corticosteroids, SCL debridement through the joint with a drill bit, translesional cortical screw placement, and absorbable hydroxyapatite implant placement. Data from 182 Thoroughbred yearlings treated for SCL in the medial femoral condyle were collected from 2014 to 2020. Limb affected, age at surgery, sex, and radiographic measurements of the SCL were recorded. Auction price and racing performance were collected for treated horses and compared to 154 maternal siblings free of medial femoral condyle SCL. Analyses were conducted to assess if racing prognosis was affected by SCL size, to detect differences in auction price and selected flat racing outcome parameters between cases and controls, and to compare racing prognosis between the studied treatments. Mares and lesions located in the right stifle were significantly overrepresented. The auction price of treated horses was significantly lower than that of their siblings. Horses treated for SCL had significantly lower chances to start in a race than controls (59% vs. 74% respectively). Wider SCL negatively affected the chances to start at least in one race, and negatively affected the earnings made in the 2-year-olds' racing year. Horses with SCL treated using a bioabsorbable implant had a significantly higher median in starts as 3-year-olds (seven starts) than horses that had the SCL debrided with a drill bit (three starts). In conclusion, Thoroughbred yearlings treated for a medial femoral condyle SCL had lower auction prices and decreased ability to start a race compared to siblings' wider cysts had worse prognosis to start a race and might affect earnings as 2-year-olds; and horses treated with bioabsorbable composite implant placement had more starts as 3-year-olds than with other techniques.

Equine subchondral lucencies: Knowledge from the medial femoral condyle

Equine subchondral lucencies (SCL) have been described since the first availability of suitable radiographic equipment. The initial clinical sign can be lameness, but SCLs are often first found on surveys of juvenile horses and are primarily a radiographic concern for public auctions. When lameness is present, it varies from subtle to obvious and can be intermittent. Some SCLs heal spontaneously, and some remain blemishes, but when the SCL and lameness are persistent, further damage to the joint and limitations to an athletic career are likely. SCLs were initially described in the distal limb followed by the stifle, and the medial femoral condyle (MFC) is now considered the most common location. The aim of this review is to highlight the initial pathology and discuss the clinical and experimental information available on equine SCLs. SCL treatment has evolved from rest alone and has progressed to debridement, grafting, intralesional injection, and most recently, transcondylar screw and absorbable implant placement. Comparison of success rates between techniques is difficult due to variations in follow-up and outcome measures, and no single technique is best for all SCLs. Treatment appears to increase success by 15%-20% over rest alone, but the method chosen depends on many factors. This review emphasizes the need for further work to fully understand SCL formation and all aspects of trabecular bone healing to optimize surgical therapy and improve treatment success.

Arthroscopically guided lag screw fixation of subchondral bone cysts in the medial femoral condyle in Thoroughbred racehorses: description of technique and comparative results

OBJECTIVE

To describe an arthroscopically guided technique for lag screw placement across subchondral bone cyst (SBC) in the medial femoral condyle (MFC) and to compare postoperative racing performance with corticosteroid injection and cyst debridement.

STUDY DESIGN

Retrospective cohort study.

ANIMALS

One hundred twenty-three horses with 134 MFC SBCs undergoing treatment at a single referral hospital in the UK between January, 2009, and December, 2020.

METHODS

Sex, age, limb affected, radiographic cyst dimensions, preoperative and postoperative lameness, surgical technique (lag screw placement, cyst debridement, intralesional corticosteroid injection), and, where applicable, screw positioning were recorded retrospectively. A ratio was calculated using measurements from preoperative and postoperative radiographs. Outcome was assessed by resolution or improvement in lameness, reduction in cyst size, and starting one race after treatment. Outcome data was compared between treatment groups.

RESULTS

Twenty-six of 45 (57.8%) horses that underwent transcondylar screw placement raced postoperatively, at a median of 403 days between surgery and first postoperative race. There was no difference between treatment groups with regard to racing or preoperative and postoperative lameness. Cysts treated with transcondylar screw placement had a greater reduction in cyst size and a reduced period of convalescence in comparison with those that underwent debridement; the results were similar to those treated by intralesional corticosteroid injection.

CONCLUSION

Postoperative racing rates were similar for all techniques. Convalescence was reduced for lag screw placement and corticosteroid injection compared to debridement.

CLINICAL SIGNIFICANCE

The arthroscopically guided technique results in radiographically consistent screw placement and cyst engagement and offers a viable alternative to other treatments.

Treatments and Prognosis for Subchondral Cystic Lesions in the Distal Extremities in Thoroughbred Prospect Racehorses

Subchondral cystic lesions (SCLs) in equines and their treatments have been mainly studied in the medial femoral condyle of the femur. SCLs in the distal extremities affecting the fetlock or interphalangeal joints are frequent, but treatment or prognosis studies in horses are currently sparse. Our objective was to compare four treatments for SCLs in the distal extremities (intralesional injection of corticosteroids, transcortical drilling, cortical screw placement, and absorbable hydroxyapatite implant placement) and report the racing prognoses for affected thoroughbred yearlings. Data from 113 thoroughbred yearlings treated for SCLs in the distal extremities were collected from 2014 to 2020. Age at surgery, sex, bone affected, radiographic SCL measurements, SCL shape, and type of treatment were recorded. Sale data and racing performance were collected for the operated horses and for 109 maternal siblings that were free of SCLs. An analysis was conducted to assess if SCL size affected racing prognosis and to detect differences in sale value and selected racing parameters between the cases and controls. The outcomes for the different treatments, the different bones affected, and the SCL shape type were also analyzed. There was no difference in the ability to start in a race between the cases and controls (60.2% vs. 69.7%, respectively). The auction value of the treated horses was significantly lower than that of their siblings. The bone affected did not impact any of the racing variables studied, whereas the height of the SCLs negatively affected the number of wins and placed races. The type of treatment for the horses affected by SCLs did not have an impact on sale prices, ability to start a race, race starts, wins, and places, or age at the time of the first start. In conclusion, yearlings diagnosed with an SCL in the distal extremities had lower auction prices and decreased racing performances, with lower numbers of wins correlated with larger SCL heights compared to the siblings. Similar racing performance was found regardless of the treatment received.

Subchondral Bone Cyst Development in Osteoarthritis: From Pathophysiology to Bone Microarchitecture Changes and Clinical Implementations

Osteoarthritis is a degenerative joint disease affecting middle-aged and elderly patients. It mainly involves weight-bearing joints such as the hip, knee and spine as well as the basilar joint of the thumb, causing dysfunction and painful symptoms. Often, joint arthritis is accompanied by cartilage defects, joint space narrowing, osteophytes, bone sclerosis and subchondral bone cysts (SBC). The aim of the present study was to explore the pathophysiology responsible for the development of SBCs as well as the association between SBCs and disease progress, the level of clinical symptoms and their impact on postoperative outcomes and risk of possible complications following joint replacements if left untreated. A literature review on PubMed articles was conducted to retrieve and evaluate all available evidence related to the main objective mentioned above. A few theories have been put forth to explain the formation process of SBCs. These involve MMPs secretion, angiogenesis, and enhanced bone turnover as a biological response to abnormal mechanical loads causing repeated injuries on cartilage and subchondral tissue during the development of arthritis. However, the application of novel therapeutics, celecoxib-coated microspheres, local administration of IGF-1 and activated chondrocytes following surgical debridement of SBCs hinders the expansion of SBCs and prevents the progression of osteoarthritis.

Differences of morphological attributes between 62 proximal and distal subchondral cystic lesions of the proximal phalanx as determined by radiography and computed tomography

OBJECTIVE

To determine morphological characteristics of subchondral cystic lesions (SCLs) in the proximal phalanx (PP) of adult horses.

SAMPLE

Radiographs and/or CT scans of PP from 46 horses.

PROCEDURES

There were horses with a SCL in PP, which was diagnosed by radiography and/or computed tomography, included. Additional data (signalment, history, orthopedic examination) were collected retrospectively for each case.

RESULTS

Forty-six horses met the required inclusion criteria, with a total of 62 SCLs. Forty-three SCLs (70.5%) were located in the proximal PP (group A). Forty-four percent of these were associated with short, incomplete fractures, while 30 of the proximal PP SCLs (69.7%) were found mid sagittal. Proximal SCLs mostly showed a blurred, irregular shape (62.8%) and long, as well as wide, but shallow shapes in CT. Eighteen SCLs (29.5%) were found in the distal PP, near the proximal interphalangeal joint (group B). In contrast to the described proximal SCLs, the distal SCLs were of circular or oval shape, well delineated (77.8%), and distinctly larger. Horses of group A were significantly older (mean age, 11.47 years) than horses of group B (mean age, 6.72 years).

CLINICAL RELEVANCE

The distribution and morphological attributes of proximal PP SCLs as well as their association to subchondral bone lesions and short, incomplete proximal fractures indicate more recently developed lesions due to chronic stress factors, such as repetitive trauma to the cartilage and subchondral bone. In contrast, morphology and distribution of distal SCLs showed high accordance with developmental bone cysts originating from a failure of endochondral ossification.

Comparative results of 3 treatments for medial femoral condyle subchondral cystic lesions in Thoroughbred racehorses

OBJECTIVES

To compare 3 different methods for treatment of medial femoral condyle (MFC) subchondral cystic lesions in Thoroughbred horses <24 months old based on the criterion of ability to race post-treatment.

STUDY DESIGN

Retrospective cohort study.

ANIMALS

Thoroughbreds (n = 107, age < 24 months) diagnosed with MFC subchondral cystic lesions.

METHODS

Medical records between January 2004 and December 2017 were reviewed. Three treatment methods were used in these horses during that time frame: arthroscopic debridement, intralesional autologous mesenchymal stem cell (MSC) injection, and intralesional corticosteroid injection. The outcome evaluated was the ability to compete in a pari-mutuel race.

RESULTS

Seventy-eight of 107 Thoroughbreds (73%) raced post-treatment; 41/57 (72%) of horses treated by arthroscopic debridement raced; 16/19 (84%) of horses treated with intralesional MSCs raced; 21/31 (68%) of horses treated with intralesional corticosteroids raced. There was no difference between groups in the ability to start a race. Sex, limb affected, and lesion size also had no effect on the ability to start a race. There was a trend for increasing lesion size reducing the probability of racing.

CONCLUSIONS

Seventy-three percent of the horses raced, but there was no difference in the ability of unraced Thoroughbreds to race after treatment of MFC subchondral cystic lesions with arthroscopic debridement, intralesional mesenchymal stem cells, or intralesional corticosteroids.

CLINICAL SIGNIFICANCE

The 3 reported treatment options may be considered for treatment of MFC subchondral cystic lesions with a good prognosis for racing post-treatment. Owners should be advised that increasing lesion size decreases the probability of racing.

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

OBJECTIVE

To determine the failure method of simulated equine medial femoral condyle (MFC) subchondral bone defects under compression and the influence of screw placement on failure resistance.

STUDY DESIGN

In vitro study.

SAMPLE POPULATION

Composite disks (CD) simulating the moduli of yearling bone in the MFC.

METHODS

Four CD conditions were tested, all with a 12.7 mm void (n = 6 per condition): intact (no void), void only, void with a 4.5 mm screw placed in neutral fashion, and void with a 4.5 mm screw placed in lag fashion. Composite disks of each condition were tested under monotonic compression to 6000 N and cyclic compression to 10 000 cycles. Observable failure, load at first observable failure, and displacement at peak 2000 N load were compared among conditions.

RESULTS

Specimens failed by cracking at the superior aspect of the void or the screw exit hole. After monotonic loading, cracks were observed 6/6 CD with a void, 6/6 CD with a void/lag screw, and 5/6 CD with a void/neutral screw. After cyclical testing, cracks were noted only on the superior aspect of 6/6 CD with a void and 3/6 CD with a void/lag screw. Displacement at peak load was 0.06 mm (intact), 0.32 mm (void), 0.24 mm (void/lag screw), and 0.11 mm (void/neutral screw).

CONCLUSION

Model MFC voids failed by superior cracking that was resisted by lag and neutral screw placement.

CLINICAL SIGNIFICANCE

Neutral screws may be an acceptable treatment for subchondral lucencies in the MFC.

Modified Proximal Interphalangeal Joint Arthrodesis in a Yearling Filly with an Osseous Cyst-Like Lesion in the Proximal Phalanx

After the medial femoral condyle (MFC), the phalanges are the second most common site for osseous cyst-like lesions (OCLLs). Conservative treatment of phalangeal cysts on the convex surface of proximal phalanx presents a technical problem with access to the stoma of the cyst. Surgical therapy options usually aim to avoid cyst enlargement through drilling or screw placement or to encourage lesion filling with osteoconductive material. This paper describes a case of treatment of the OCLL in a yearling Czech warmblood filly with surgical arthrodesis, together with the packing of the OCLL with calcium phosphate biocement (CPB). The filly showed a chronic, moderate to severe, intermittent left hindlimb lameness. Dynamic examination combined with regional anesthesia and radiography confirmed a clinically significant large OCLL on the distal joint surface of the first phalanx. Treatment of the OCLL was performed by surgical arthrodesis of the proximal interphalangeal joint, using two paraxial and one axial crossed lag screw, after curetting of the cyst and filling with CPB.

Management of Subchondral Lucencies of the Medial Aspect of the Equine Antebrachiocarpal Joint

The objective of this study is to describe the management and outcomes of eight horses with subchondral lucencies (SCLs) of the medial aspect of the antebrachiocarpal (ABC) joint. The medical records and radiographs of the carpi of 8 horses with SCLs of the medial aspect of the ABC joint were reviewed. Follow-up clinical information was obtained for 6-60 months (the median duration of 14 months). Treatment was successful if radiographic healing was apparent or lameness was reduced or eliminated. Four horses had SCLs in the distomedial radius (DMR) and four in the proximal aspect of the radiocarpal bone (RCB). Lameness was present in all horses with DMR SCLs and in one horse with an RCB SCL. Treatments included restriction of exercise (n = 3), intra-articular administration of corticosteroids (n = 2), or placement of a screw across the SCL (n = 3). Exercise restriction alone was successful in three nonlame horses younger than one year with proximal RCB SCL and intra-articular corticosteroid administration in the ABC joint in two horses aged 2 years or younger with DMR SCLs. A yearling with a large proximal RCB SCL and two horses aged 5 years or older with DMR SCLs were successfully treated with screw placement across the SCL. Exercise restrictions and intra-articular administration of corticosteroids were successful in management of DMR SCLs in five horses. Placing a screw across the SCL of three horses resulted in resolution of lameness and substantial improvement of the radiographic appearance of the lesion in the RCB or DMR.

Progression of shallow medial femoral condyle radiographic lucencies in Thoroughbred repository radiographs and their influence on future racing careers

BACKGROUND

Shallow lucencies less than 4 mm deep into the medial femoral condyle (MFC) are frequent in Thoroughbred horses undergoing screening sales radiographs. It is unclear if these shallow defects are precursors to larger cystic lesions or if they are fully developed defects that remodel into a flattened femoral condyle.

OBJECTIVE

To evaluate radiological lucencies of the MFC and their progression in size, in a cohort of Thoroughbred horses, ranging from 5 to 18 months of age and to report on the racing careers of these horses compared to their maternal siblings free of stifle pathology.

STUDY DESIGN

Retrospective cohort.

METHODS

Radiographic reports were reviewed to identify cases with MFC lucency. Medical data including age at the time of radiographic sale set, sex, and MFC lucency radiographic measurements were recorded. The data were analysed for changes in lucency morphology. Racing data were collected and analysed for the following 5 years.

RESULTS

From 12 938 sales reports reviewed, 3874 horses were found to have radiographic sets available at both weanling and yearling sales. A MFC lucency ≤3 mm in depth was diagnosed in at least one radiographic sales set in 248 horses (6.4%). The right femur was more commonly affected (73.9%) than the left. Radiographic lucencies in the left femur were significantly smaller (P = .02) than lucencies in the right femur. Radiographic lucencies resolved in 6.1% of cases, 3.6% of cases developed into a cyst, 40.7% of cases were unchanged in size, 23.6% of lucencies decreased in size and 8.2% increased in size. Cysts >3 mm deep regressed into smaller lesions accounting for 4.9% of the lucencies, and 12.9% of lucencies developed from a normal or flat medial femoral condyle contour. Horses with a medial femoral condyle lucency had significantly less starts as a 2-year-old vs. their maternal siblings (P < .01).

MAIN LIMITATIONS

Data were collected retrospectively. Measurement errors may have occurred due to the measuring tool scale, small size of the defects and/or radiographic position. Treatments between radiographic studies were unknown and could not be accounted for. Observers were not blinded to radiographic sales reports.

CONCLUSIONS

Radiographically diagnosed lucencies in the MFC of immature Thoroughbreds have the potential to fully resolve or develop into a cyst. However, most radiographic lucencies do not change in size. Thoroughbreds with MFC lucencies had less starts as 2-year-olds when compared to their maternal siblings free of stifle pathology.

Impact of Size and Shape of Equine Femoral Subchondral Bone Cysts With a Transcondylar Screw on Predicted Bone Formation Area in a Finite Element Model

Equine subchondral bone cysts (SBCs) develop most often in the medial femoral condyle (MFC) of yearlings intended for performance. SBCs often cause lameness and can cause secondary injuries to the meniscus and tibial cartilage. A novel surgical technique using a transcondylar lag screw (TLS) across an MFC SBC has shown success in lameness resolution and radiographic healing of MFC SBC. In a previous study using finite element analysis, our lab showed that a TLS stimulated bone formation on the inner surface of the SBC and altered third principal stress vectors to change the direction of surface compression to align with the screw axis. This work extended the previous study, which was limited by the use of only one idealized SBC. Our objective was to test SBCs of several sizes and shapes in a newly developed equine stifle FEM with a TLS to determine how cyst size affects bone formation stimulation. This study found that a transcondylar screw is most effective in stimulating bone formation in cysts of greater height (proximal-distal). The TLS increases stress stimulus in the bone around the cyst to promote bone apposition and directs compression across the cyst. If full penetration of the screw through the cyst is possible, it is recommended that the transcondylar screw be used to treat subchondral bone cysts. For the treatment of smaller cysts that are not accessible by the current screw surgical approach, future work could study the efficacy of a dual-pitch headless screw that may reach smaller cysts.

Subchondral lucencies of the proximal tibia in 17 horses

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.

Long-term outcome after stifle arthroscopy in 82 Western performance horses (2003-2010)

OBJECTIVE

To report the outcome of horses engaged in Western performance disciplines after stifle arthroscopy and identify prognostic factors for return to performance.

STUDY DESIGN

Retrospective case series.

SAMPLE POPULATION

Eighty-two Western performance horses undergoing stifle arthroscopy.

METHODS

Medical records were reviewed for horses involved in athletic performance/training for various Western performance disciplines and undergoing arthroscopy for lameness localized to the stifle. Follow-up was obtained ≥2 years postoperatively by telephone interviews with the owners. Preoperative and intraoperative findings as well as postoperative treatment were analyzed for their association with return to athletic performance as the primary outcome of interest.

RESULTS

The most common disciplines represented were cutting (n = 38), Western pleasure (n = 13), and reining (n = 13). Approximately 40% (32/82) of horses returned to intended use after surgery. Increased age, higher degree of lameness, longer duration of lameness, and the presence of partial-thickness cartilage lesions decreased the odds of returning to athletic performance. Postoperative therapies (intra-articular: stem cells, corticosteroids, interleukin-1 receptor antagonist protein, hyaluronic acid/polysulfated glycosaminoglycans; systemic: nonsteroid anti-inflammatory drugs, hyaluronic acid/polysulfated glycosaminoglycans, oral joint supplements) did not affect the odds of returning to intended use.

CONCLUSION

Less than half of the Western performance horses that underwent stifle arthroscopy returned to intended use. Older age, longer duration of lameness, and presence of partial-thickness cartilage lesions affected the odds of a horse returning to intended use. Postoperative therapies did not affect the outcome in this population.

CLINICAL SIGNIFICANCE

The prognosis of Western performance horses undergoing stifle arthroscopy is as guarded as that previously reported in horses of other disciplines.

Surgical Treatment of an Osseous Cyst-Like Lesion in the Middle Phalanx Communicating With the Distal Interphalangeal Joint of a Horse

Subchondral or osseous cyst-like lesions within the distal aspect of the middle phalanx are not commonly reported in equids. These osseous lesions, which can communicate with the distal interphalangeal joint, can result in significant lameness and may not respond well to medical management. This report describes the clinical, diagnostic imaging, and surgical management of a 4-year-old mixed breed gelding where medical management of a chronic subchondral osseous cyst-like lesion of the middle phalanx, which communicated with the distal interphalangeal joint, was unsuccessful. A successful outcome was accomplished after surgical cyst debridement and packing with tricalcium phosphate, a bone marrow aspirate, and platelet-rich plasma.

A comparison of arthroscopy to ultrasonography for identification of pathology of the equine stifle

REASONS FOR PERFORMING STUDY

To evaluate and compare the diagnostic capability of arthroscopy and ultrasonography for the detection of pathological change in equine stifle joints. Although descriptions of the arthroscopic and ultrasonographic boundaries of the normal femorotibial joint exist, there are few examples in the literature comparing the pathological changes observed with each imaging modality.

OBJECTIVES

To evaluate and compare arthroscopic and ultrasonographic examinations for characterising pathological change in the stifle joint. To describe how the results of arthroscopic and ultrasonographic examinations may differ in characterising the severity of lesions and to evaluate which lesions are best assessed with each modality.

STUDY DESIGN

Retrospective review of ultrasonographic and arthroscopic examinations.

METHODS

The structures of the stifle joint were evaluated and graded for pathological change by scoring arthroscopic and ultrasonographic examinations. The presence and severity of the lesions were then compared between each modality.

RESULTS

Medial meniscal lesions were detected more often with ultrasonography than with arthroscopy. Conversely, arthroscopy was better for detection of cranial medial meniscotibial ligament (CrMMTL) tearing. Articular cartilage defects were best detected with arthroscopy and periarticular osteophytes of the medial femoral condyle with ultrasonography. Four cases had defects within one of the patellar ligaments, all of which were only characterised with ultrasonography.

CONCLUSIONS

Ultrasonography and arthroscopy should be combined to best evaluate pathology of the stifle, since each modality has its own limitations depending on the location and type of lesion.

Focal defect resembling a subchondral bone cyst of the ulnar trochlear notch in a dog

A 13 mo old spayed female golden retriever/standard poodle mixed-breed dog was presented for intermittent right forelimb lameness. Physical examination revealed marked effusion and decreased flexion in the right elbow joint, radiography showed mild osteophytosis of the right elbow joint, and computed tomography showed a focal defect in the subchondral bone in the trochlear notch of the ulna resembling a subchondral bone cyst. Arthroscopy of the affected elbow revealed a focal defect in the articular cartilage on the trochlear notch with vascular ingrowth covering a defect in the subchondral bone plate. The synovium surrounding the defect was inflamed. To the authors' knowledge, this is the first published report of a subchondral bone cyst in the ulna of a dog.

Clinical outcome after intra-articular administration of bone marrow derived mesenchymal stem cells in 33 horses with stifle injury

OBJECTIVE

To report outcome of horses with femorotibial lesions (meniscal, cartilage or ligamentous) treated with surgery and intra-articular administration of autologous bone marrow derived mesenchymal stem cells (BMSCs).

STUDY DESIGN

Prospective case series.

ANIMALS

Horses (n = 33).

METHODS

Inclusion criteria included horses that had lameness localized to the stifle by diagnostic anesthesia, exploratory stifle arthroscopy and subsequent intra-articular administration of autologous BMSCs. Case details and follow-up were gathered from medical records, owner, trainer or veterinarian. Outcome was defined as returned to previous level of work, returned to work, or failed to return to work.

RESULTS

Follow-up (mean, 24 months) was obtained; 43% of horses returned to previous level of work, 33% returned to work, and 24% failed to return to work. In horses with meniscal damage (n = 24) a higher percentage in the current study (75%) returned to some level of work compared to those in previous reports (60-63%) that were treated with arthroscopy alone, which resulted in a statistically significant difference between studies (P = .038). Joint flare post injection was reported in 3 horses (9.0%); however, no long-term effects were noted.

CONCLUSIONS

Intra-articular administration of BMSC postoperatively for stifle lesions appeared to be safe, with morbidity being similar to that of other biologic agents. Improvement in ability to return to work may be realized with BMSC treatment compared to surgery alone in horses with stifle injury.

Arthroscopic approach and intraarticular anatomy of the stifle in South American camelids

OBJECTIVE

To describe a cranial arthroscopic approach to the stifle of South American camelids and to report our clinical experience with camelid stifle arthroscopy.

STUDY DESIGN

Experimental study and retrospective case series.

ANIMALS

(1) Cadaveric alpaca hindlimbs (n = 18; 9 alpacas); (2) 1 alpaca and 1 llama

METHODS

Polymethylmethacrylate joint casts (n = 2) were made to define stifle joint dimensions. Cadaveric stifle joints (n = 16) were evaluated arthroscopically to determine arthroscopic portal locations, describe the intraarticular anatomy, and report potential complications. An alpaca and a llama with stifle joint disease had diagnostic arthroscopy.

RESULTS

Successful entry into the stifle joint was achieved in 16 cadaver limbs. Observed structures were: the suprapatellar pouch, articular surface of the patella, femoral trochlear ridges and groove, cranial aspect of the femoral condyles (n = 16); distal aspect of the cranial and proximal aspect of the caudal cruciate ligaments (14); and cranial aspects of the medial and lateral menisci (11), and cranial meniscotibial and intermeniscal ligaments (8). Stifle arthroscopy allowed for joint evaluation and removal of osteochondral fragments in 1 alpaca and 1 llama with naturally occurring stifle disease. Complications of cadaver or live procedures included minor cartilage scoring (3 stifles) and subcutaneous periarticular fluid accumulation (8 stifles).

CONCLUSIONS

Arthroscopy provides a safe approach for diagnosis and treatment of stifle lesions in South American camelids.