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Abstract

Objective—To characterize discrete palmar carpal osteochondral fragmentation in horses and to document the effect of osteoarthritis and surgical removal of these fragments on functional outcome.

Design—Retrospective case series.

Animals—25 horses.

Procedures—Medical records and radiographic views were reviewed to identify horses that had radiographic evidence of palmar carpal fragmentation, which was subsequently treated by arthroscopic removal. Information collected included cause of fracture, initial and long-term clinical and radiographic findings, and functional outcome.

Results—Palmar carpal fragmentation of 30 carpal bones was identified in 25 unilaterally affected horses. A known traumatic event was reported to cause the fragmentation in 17 of the 25 (68%) horses. Of the 25 horses, 17 (68%) had fragmentation involving the antebrachiocarpal joint, 7 (28%) had fragmentation involving the middle carpal joint, and 1 (4%) had fragmentation involving the carpometacarpal joint. The proximal aspect of the radial carpal bone was the most commonly affected site (12/30 fragments), followed by the accessory carpal bone (6/30). Of the 25 horses, 19 (76%) were not lame (sound) after surgery and returned to their intended use, 4 (16%) were considered pasture sound, and 2 were euthanized (because of severe postoperative osteoarthritis or long bone fracture during recovery from anesthesia). Eight of the 14 horses with preoperative evidence of osteoarthritis returned to function after surgery. Twelve of 17 horses with antebrachiocarpal joint fragments and 6 of 7 horses with middle carpal joint fragments returned to their previous use.

Conclusions and Clinical Relevance—Results indicated that the prognosis for horses after arthroscopic removal of palmar carpal osteochondral fragments is good. Early intervention, before the development of osteoarthritis, is recommended.

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in Journal of the American Veterinary Medical Association

Abstract

Objectives—To define a portion of the nucleotide sequences of each of the 6 insulin-like growth factor (IGF) binding proteins (IGFBPs) in horses and describe patterns of messenger RNA (mRNA) and protein expression for IGFBPs in normal equine tendons.

Animals—7 horses.

Procedure—Total RNA was extracted from the tensile region of normal superficial digital flexor tendons and reverse transcribed into complimentary DNA (cDNA). The cDNA was amplified via PCR, and products representing portions of each IGFBP were cloned and sequenced. Nucleotide sequences were used to deduce the amino acid sequences, and both nucleotide and predicted amino acid sequences were compared with those published for bovine, human, mouse, and ovine IGFBPs. Gene expression was quantitated by real-time PCR assay, and protein expression was evaluated by western ligand blot (WLB).

Results—Clones ranged in size from 262 to 522 bp and had high degrees of sequence homology with other mammalian species. Sequence homology was highest between bovine and equine IGFBPs (86% to 95%) and amongst the IGFBP-5 sequences from the various species (92% to 95%). Message for IGFBP-2 to -6, but not IGFBP-1, was expressed in normal tendon. Protein expression for IGFBP-2, -3, and -4 was detected by WLB in normal tendon and markedly increased in damaged tendons.

Conclusions and Clinical Relevance—Results provide basic information and tools needed for further characterization of the role of the IGF system in tendon healing and may lead to the ability to potentiate the response of healing tendon to exogenous IGF-I via concurrent manipulation of IGFBPs. (Am J Vet Res 2005;66:300–306)

Full access
in American Journal of Veterinary Research
History

A 2-year-old Quarter Horse gelding was referred to the Cornell University Hospital for Animals with a 5-week history of repeated episodes of stumbling and occasionally falling during exercise. On neurologic examination, both mentation and cranial nerve function were normal. Substantial ataxia and proprioceptive deficits were present in both the pelvic (3/4) and thoracic limbs (2/4),1 characterized by profound circumduction of the outside limb when circling, a hypermetric gait, and a marked worsening of clinical signs when the horse's head was elevated, leading to a neuroanatomic diagnosis of cervical spinal cord disease. There were moderate signs of pain

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To clarify the diagnosis of avulsion of the lateral palmar intercarpal ligament (LPICL), correlate avulsion of this ligament with lameness, determine the prevalence of avulsion of the LPICL in a hospital population, and evaluate the response to surgical removal of the avulsion fragment in horses.

Design—Retrospective study.

Animals—37 horses with avulsion of the LPICL.

Procedure—Medical records and radiographs of horses with avulsion of the LPICL were reviewed; follow-up information was obtained from race records and from owners via a telephone survey.

Results–Of 6,418 horses evaluated for forelimb lameness from March 1, 1990, to December 31, 2001, 37 (0.5%) had avulsion of the LPICL; each horse had a discrete fragment associated with avulsion of the ligament origin from the ulnar carpal bone. Twenty-six horses underwent arthroscopic fragment removal; 20 of 22 (91%) horses for which follow-up information was available returned to work. Of 9 horses treated conservatively, 5 returned to work. Odds ratio calculations indicated that horses treated surgically were 8 times as likely to return to work than those not treated surgically. Twelve horses had LPICL avulsion without concurrent osteochondral fragmentation in the same or additional joints; follow-up information was available for 9 of those horses, of which 8 returned to athletic work.

Conclusions and Clinical Relevance—In horses, discrete avulsion of the LPICL can be a cause of lameness and arthroscopic debridement may be the treatment of choice. Prognosis for return to work of horses with avulsion of the LPICL is good. (J Am Vet Med Assoc 2005;226:760–766)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate the effects of recombinant human platelet–derived growth factor-BB (rhPDGF-BB) on the metabolic function and morphologic features of equine superficial digital flexor tendon (SDFT) in explant culture.

Animals—6 euthanized horses (2 to 5 years old).

Methods—Forelimb SDFT explants were cultured for 6 days as untreated control specimens or treated with rhPDGF-BB (1, 10, 50, or 100 ng/mL of medium). Treatment effects on explant gene expression were evaluated via real-time PCR analysis of collagen type I, collagen type III, PDGF-A, and PDGF-B mRNA. Explants were assayed for total collagen, glycosaminoglycan, and DNA content; histologic changes were assessed via H&E staining and immunohistochemical localization of collagen types I and III.

Results—No morphologic or proliferative changes were detected in tendon explant sections. After high-dose rhPDGF-BB treatment, gene expression of collagen types I and III was increased and decreased, respectively. Expression of PDGF-A and PDGF-B mRNA was significantly increased at 24 hours, but later decreased to have few or negative autoinductive effects. Although PDGF gene expression waned after 48 hours of culture, collagen type I gene expression was significantly increased at 48 hours and reached peak value on day 6. Glycosaminoglycan and DNA content of explants were unchanged with rhPDGF-BB treatment.

Conclusions and Clinical Relevance—Results suggest that rhPDGF-BB use may be of benefit in the repair of equine tendon, particularly through induction of collagen type I mRNA. Positive autoinductive effects of PDGF-BB in equine SDFT explants were detected early following culture medium supplementation, but these diminished with time.

Full access
in American Journal of Veterinary Research

Abstract

Case Description—3 horses were referred for treatment of subchondral cystic lesions of 1 or both medial femoral condyles.

Clinical Findings—All horses had clinically apparent lameness confirmed to be due to a radiographically evident subchondral cystic lesion of the medial femoral condyle with a large articular component (> 15 mm) and shallow subchondral depth (< 10 mm). Arthroscopic assessment of affected cartilage revealed undulating cartilage with a relatively smooth surface and extensive residual perimeter attachment.

Treatment and Outcome—Resorbable polydioxanone pins were used arthroscopically to reattach the cartilage overlying the subchondral cystic lesions. A biologic graft (bone marrow aspirate concentrate or allogeneic chondrocytes) was injected into the depths of the cystic cavity following cartilage reattachment. Follow-up examination confirmed radiographic resolution of the lesion and elimination of clinical signs within the treated femorotibial joint.

Clinical Relevance—Lesions with a large area of affected articular cartilage have been associated with a decreased rate of return to athletic function following arthroscopic debridement, likely secondary to the loss of subchondral architecture and the production of imperfect fibrocartilage repair. Salvage of the affected cartilage in a select population of horses with progressively expanding but shallow subchondral cystic lesions of the medial femoral condyle is possible and may improve radiographic and clinical outcome.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the clinical, radiographic, ultrasonographic, and arthroscopic findings associated with tenosynovitis of the carpal synovial sheath induced by exostoses that originate from the caudal surface of the physeal scar of the distal radius and determine the results of surgical removal of those exostoses in horses.

Design—Retrospective study.

Animals—10 horses.

Procedure—Medical records of horses with effusion in the carpal synovial sheath and lameness evaluated from 1999 to 2003 were examined.

Results—All horses had a history of intermittent mild to moderate effusion of the carpal synovial sheath and lameness of 1 forelimb. Results of regional perineural and intrathecal anesthesia of the carpal synovial sheath confirmed that the lameness originated in the carpal synovial sheath. Radiography revealed exostoses originating from the caudal cortex of the distal radius at the level of the closed physis. Arthroscopy was performed for confirmation and removal of exostoses that penetrated the carpal synovial sheath and impinged on the deep digital flexor tendon. All horses returned to previous athletic activity. One horse had a recurrence of clinical signs 12 months after surgery, which resolved with medical treatment.

Conclusions and Clinical Relevance—Tenosynovitis of the carpal synovial sheath and lameness were caused by impingement of exostoses of the caudal radius on the lining and contents of the carpal synovial sheath. Although the clinical signs and surgical treatment were similar to that caused by osteochondromas, these exostoses developed at the level of the closed physis of the distal radius and were not radiographically or histologically similar to osteochondromas. (J Am Vet Med Assoc 2004;224:264–270)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To clone the 5' end of type III collagen and describe its pattern of mRNA and protein expression in normal and healing tendons in horses.

Animals—14 healthy adult horses.

Procedure—The tensile region of collagenase-injured superficial digital flexor tendons was harvested at intervals from 1 to 24 weeks after injury. Total RNA was reverse-transcribed into cDNA for cloning and sequencing of type III collagen. Equine-specific nucleic acid probes were developed and used for northern blot analysis and in situ hybridization. Type III collagen protein and cyanogen bromide-cleaved collagen peptides were assessedby gel electrophresis.

Results—Type III collagen mRNA expression and protein content increased immediately after injury and remained increased. Type III collagen was localized to the endotenon in normal tendon and in injured tendon at 1 week. At 8 and 24 weeks, expression became more widely distributed throughout the tendon parenchyma. Injured tendon contained 6 times more type I than type III collagen mRNA. Quantities of type III collagen protein were maximal in the first 4 weeks after injury (approx 33%) and then began to decrease.

Conclusions and Clinical Relevance—Type III collagen expression is increased initially in endotenon and subsequently in parenchyma of healing tendon; however, type III remains the minor collagen throughout the healing process. The role of type III collagen in tendon healing is not fully elucidated. (Am J Vet Res 2005;66:266–270)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To investigate effects of β-aminopropionitrile and a combination of insulin-like growth factor (IGF)-I and β-aminopropionitrile on metabolism of equine tendon fibroblasts.

Sample Population—Flexor tendon explants from 3 horses.

Procedure—Explants received 1 of 4 treatments (control, IGF-I, β-aminopropionitrile, and IGF-I/β-aminopropionitrile) for 10 days, and message expression for collagen types I and III was assessed by use of in situ hybridization. Histologic findings, new protein production, and quantitative determinations of glycosaminoglycan, DNA, and de novo collagen synthesis were made.

Results—Insulin-like growth factor-I stimulated an anabolic response in tendon. Collagen synthesis and glycosaminoglycan and DNA content of explants were all increased. β-Aminopropionitrile significantly suppressed collagen synthesis, which was not ameliorated by concurrent IGF-I treatment. β-Aminopropionitrile caused alterations in cell morphology characterized by large round cells with eccentric nuclei and decreased density of collagen fibers. Protein production and collagen type-III mRNA expression were reduced in these cells.

Conclusion and Clinical Relevance—Treatment with β-aminopropionitrile resulted in decreased production of protein and collagen synthesis, which could be expected to suppress tendon healing. The negative effects of β-aminopropionitrile could not be abrogated by addition of IGF-I to the medium. Treatment resulted in alterations in cell morphology and matrix consistency, which could further delay tendon healing. β-Aminopropionitrile may impair tendon healing at a cellular level by decreasing collagen production or increasing rate of degradation of existing matrix. Because of reduced crosslinking during β- aminopropionitrile treatment, in combination with transiently decreased tensile strength, alterations in collagen content and structure may weaken the healing tendon. (Am J Vet Res 2001;62:1557–1562)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the mRNA expression of bone morphogenetic protein (BMP)-6 and -2 and a BMP antagonist (Noggin) in horses with osteochondrosis.

Sample Population—Samples of articular cartilage from affected stifle or shoulder joints of 10 immature horses with naturally acquired osteochondrosis and corresponding joints of 9 clinically normal horses of similar age; additionally, samples of distal femoral growth plate cartilage and distal femoral articular cartilage were obtained from a normal equine fetus.

Procedure—Cartilage specimens were snap-frozen in liquid nitrogen, and total RNA was isolated. Adjacent specimens were fixed in 4% paraformaldehyde for histologic examination. Expression of BMP-6, BMP-2, and Noggin mRNA was evaluated by real-time quantitative polymerase chain reaction (PCR) assays. Spatial tissue mRNA expression of BMP-6 was determined by in situ hybridization.

Results—Nucleotide sequences were obtained for portions of the BMP-6 propeptide and mature peptide region, as well as the signal and mature peptide region of Noggin. Expression of BMP-6, BMP-2, and Noggin mRNA was found to be similar in cartilage from normal and osteochondrosis-affected horses. Spatial expression of BMP-6 correlated with the middle and deep layers of articular cartilage; no differences were observed in overall expression between cartilage specimens from the 2 groups of horses. No expression of BMP-6 was found in the superficial layer, subchondral bone, or osteochondrosis-affected cleft fibrous tissue.

Conclusions and Clinical Relevance—Although these signaling peptides may play important roles in cartilage differentiation, results did not provide evidence to suggest that they are involved in the disease process of osteochondrosis. (Am J Vet Res 2004;65:110–115)

Full access
in American Journal of Veterinary Research