34th Annual Scientific Meeting proceedings

Introduction

A Kerf Cylinder Implant use in equine cervical fusions as a treatment for spinal cord compression was first described in i982 ( DeBowes et al). It provided a more efficient method for arthrodesis of the intervertebral space(s) as the harvesting of a bone dowel to complete the Cloward procedure was no longer necessary. It also decreased the morbidity of a second incision if a homologus graft was used or the creation of a bone bank if an autologous dowel was used. The stainless steel perforated cylinder (Bagby Basket ) also reduced the number of sequalae (often fatal) that occurred during the early phases of the fusion process if the patient had a traumatic incident such as difficult recovery from surgery.

Later two human orthopedic surgeons ( Bagby and Kursher) designed the BAK implant that was a Kerf Cylinder that was threaded and screwed into the pre tapped site instead of hammering the implant. The force needed to hammer in the Kerf Cylinder could result in microfractures in the osteoporotic bone of older patients. The first adaption of the BAK implant for the horse ( Seattle Slew implant) had low relief threads and had a number of cases that were not secure and backed out. Many times the implant had to be threaded and hammered into place to be secure so fractures especially on older patients was still possible. The addition of higher relief threads and pretapping significantly reduced the number of fractures and backing out of the implants (Trostle). The first Seattle Slew implants were made of stainless steel but since 2007 they have been made of titianium to take advantage of the roughened surface of titanium which should increase the surface area of boney ingrowth.

We have used the basic Cloward technique with Kerf Cylinders on fetlocks, pastern and hocks on a small number of horses as a proof of concept for the fetlock, pastern and hock. The technique should be able to reduce the operative time, size of implants, comparable stability to Locking plates and a reduction in the stability that other methods have.

A Modified Cloward's Technique for Arthrodesis of the Normal Metacarpophalangeal Joint in the Horse
GREGORY R. CRAWLEY, DVM, MS, BARRIE D. GRANT, DVM, MS, DiplomateACVS, KARL K. WHITE, DVM, DiplomateACVS, DAVID D. BARBEE, DVM, MS, DiplomateACVR, ANTHONY M. GALLINA, DVM, PhD, and MARCH. RATZLAFF, DVM, PhD

A modified Cloward's technique was performed for arthrodesis of one metacarpophalangeal (MCP) joint in eight horses. Dorsal arthrotomies were performed medial and lateral to the common digitalextensor tendon and two 16 mm holes were drilled through the joint. A perfor­ atedcylindrical stainless steelbasket filled withcancellous bone wasimpactedinto eachhole. The limbs were supported in casts for B weeks. The joints were examined and radiographed at 4 weeks, 8 weeks, 6 months, and 10 months. One horse was euthanatized at week 14 to assess the progress of the arthrodesis. In the other seven horses, there was clinical fusion at month 6. Dynamographic evaluations were performed 11 months after surgery at the walk and trot. The maximum vertical forces exerted during weight bearing by treated and control limbs were compared. No difference was detected at the walk; however, a significant difference was present at the trot (p < 0.05).It was calculated that at the trot the horses placed 90% as much force on the treated limb as on the control limb. Eleven months after surgery, the baskets contained compact and cancellous bone. Ingrowth of bone occurred through all openings, completely filling the baskets and fusing the joints.

Figure 5-Typical load deformation in a representative cycle from progressive nondestructive bending in the dorsoplantar direction, where load is expressed as the bending moment, for DKC (solid black line), DMLCP (solid gray line), MLKC (dotted black line), and surgical drilling (dotted gray line) constructs created in equine tarsus specimens (n = 6/construct type). The slope of the straight region of these curves represents the stiffness. The gradient of the surgical drilling group is less than the gradients of the 3 implant groups (DKC, DMLCP, and MLKC).

Fig. 1. The double drill guide positioned over the dorsal aspect of the metacarpophalangeal (MCP) joint. Its four legs aid in correctly po­ sitioning the guide (small arrowheads). The 4.5 mm guide hole is drilled on the dorsoproximal aspect of the first phalanx (P1) (large arrow­ head).

In vitro biomechanical evaluation of four surgical techniques for fusion of equine centrodistal and tarsometatarsal joints

Adam H. Biedrzycki DVM, PhD, Barrie G. Grant DVM, Brett Nemke MS, Samantha L. Morello DVM, Mark D. Markel DVM, PhD

OBJECTIVE

To evaluate the biomechanical properties of 4 methods for fusion of the centrodistal and tarsometatarsal joints in horses and compare them among each other and with control tarsi.

SAMPLE

24 sets of paired tarsi without substantial signs of osteoarthritis harvested from equine cadavers.

PROCEDURES

Test constructs (n = 6/cype) were prepared from I tarsus from each pair co represent surgical drilling; 2 medially to laterally placed kerf-cut cylinders (MLKCs); a single large, dorsally applied kerf-cut cylinder (DKC); and a dorsomedially applied locking compression plate (DMLCP). Constructs and their contralaceral control tarsi were evaluated in 4-point bending in the dorsoplantar, lateromedial, and mediolateral directions; internal and exter­ nal rotation; and axial compression. Bending. torsional, and axial stiffness values were calculated.

RESULTS

Mean stiffness values were consistently lower for surgical drilling constructs than for contralateral control tarsi. Over all biomechanical testing, surgical drilling significantly reduced joint stability. The MLKC constructs had supe­ rior biomechanical properties co those of control tarsi for 4-poinc bending but inferior properties for external and internal rotation. The DMLCP and DKC constructs were superior to control tarsi in dorsoplantar, rotational, and axial compression directions only; DMLCP constructs had no superior stiffness in lateromedial or mediolateral directions. Only the DKC con­ structs had greater stiffness in the mediolateral direction than did control tarsi. Over all biomechanical testing, DMLCP and DKC constructs were superior to the other constructs.

CONCLUSIONS AND CLINICAL RELEVANCE

These biomechanical results suggested that a surgical drilling approach co joint fusion may reduce tarsal stability in horses without clinical osteoar­thritis, compared with stability with no intervention. whereas the DML­ CP and DKC approaches may significantly enhance stability. (Am J Vet Res 2016;77:1071-1081)

Hocks continued:

There are a number of techniques that are described for the treatment of DJD of the distal hock joints including drilling, laser debridement, medial plate compression and the use of a kerf cylinders(KCC) without threads from the medial aspect on a small number of normal horses (n=4). One smaller diameter(9mm od) implant was used in each distal joint and had to be hammered into place.

The experimental horses with the KCC did achieve arthrodesis but had prolonged discomfort and this would discourage bilateral surgery

Arthrodesis of the equine centrodistal and tarsometatarsal joints using a single modified Kerf-cut cylinder.
Adam H. Beidrzycki, Barrie D Grant, Brett Nemke, Samantha L. Morello, Mark D.Markel.

4 normal horses with Dorsal approach with minimal discomfort post op ( turned out at 4 weeks) and excellent fusion at 8 and 12 weeks with osseous fusion .

In vitro biomechanical evaluation of four surgical techneques for fusion of equine centrodistal and tarsometatarsal joints.
Adam H. Beidrzycki, Barrie D Grant, Brett Nemke, Samantha L. Morello, Mark D.Markel.

1. Drilling using 3 divergent 4.5 mm drill holes
2. Single KCC ,medial to lateral KCC (MLKCs) two threaded 12 mm OD X 35mm
3. Single large dorsally applied KCC ( DKC) 22mm OD threaded X 15mm.
4. Dorsomedially applied locking compression T plate ( DMLCP)6 holes 44mm long.

Conclusion that techniques 1 and 2 produced instability but 3 and 4 significantly enhanced stability.

Arthrodesis of the equine centrodistal and tarsometatarsal joints using a single modified kerf-cut cylinder
Adam H. Biedrzycki'; Barrie D. Grant'; Brett Nemke³; Mark D. Markel'; Samantha L. Morello'
¹Department of Large Animal Clinical Sciences College ofVeterincryMedicine, University of Florida, Gainesville, Florida, USA; ²Barrie Grant Referral Services, Bonsall, California, USA; ³ComparativeOrthopaedic Research Laboratory, School of Veterinary Medicine. University of Wisconsin-Madison,Madison. Wisconsin, USA

Summary

Objectives: To describe a technique for sur­gical placement of a modified kerf-cut cylin­ der for the purpose of arthrodesis across the equine centrodistal and tarsometatarsal joints.

Methods: Each horse (n = 4) underwent uni­lateral placement of a single kerf-<:ut cylinder spanning the centrodistal and tarsometatar­ sal joints with the placement of an autolo­ gous cancellous bone graft. Horses were evaluated via lameness examination and radiography postoperatively and euthanatiz­ ation of each horse was performed at four different time points up to 12 weeks post­ surgery to evaluate for lameness, implant stability and success with integration in the surrounding bone.

Results: Implants were placed successfully in three of four horses. In one horse, due to technical error, the implant was misaligned with the joint spaces. Although the horse ex­ hibited minimal pain. it was euthanatized at the two week follow-up. Implant placement in the remaining three horses was success­ fully achieved. At eight weeks, radiographi­ cally there was evidence of osseous union across the joint spaces. No change in lame­ ness was detected at any point after surgery. At 12 weeks post-surgery, histologically the implants were filled with mineralized osteoid and demonstrated integration with the sur­ rounding tissue.

Clinical significance: The surgical approach

and placement of modified kerf-cut cylinders for arthrodesis of the centrodistal and tar­ sometatarsal joints were successfully achiev­ ed with minimal signs of postoperative pain and a short rehabilitation time period in nor­mal horses.

Arthrodesis of the equine distal tarsal joints by perforated stainless steel cylinders
R. M. ARCHER*, R. K. SCHNEIDERt, W. A. LINDSAY and J. W. WILSON
Department of Surgical Sciences, School of Veterinary Medicine University of Wisconsin-Madison, 2015 Linden Drive W, Madison, Wisconsin 53706, USA

Summary

Perforated stainless steel cylinders filled with autogenous cancellous bone were implanted in the distal tarsaljointsoffour horses. Graft cell survival was poor two weeks after surgery in one horse. In two horses, at 10 months there was partial arthrodesis of the joints with incorporation of the implants into the osseous union. The implants were filled with vascularised woven bone. These two horses were sound nine months after surgery. One horse fractured its third tarsal bone and was still positive to a hock flexion test 12 months after surgery.

Arthrodesis of the Equine Proximal Interphalangeal Joint: A Biomechanical Comparison of Two Parallel Headless, Tapered, Variable-Pitched, Titanium Compression Screws and Two Parallel 5.5 mm Stainless-Steel Cortical Screws
RYAN R. E. WOLKER, DVM, MVetSc, JAMES L CARMALT, MA, VetMB, MVetSc, Diplomate ABVP & ACVS, and DAVJD G. WILSON, DVM, Diplomate ACVS

Objective-To compare the biomechanical characteristics, failure mode, and effects of side (left or right limb) and end (forelimb or hindlimb) of different screws in 2-screw, parallel- crew proximal interphalangeal joint arthrodesis constructs in horses.

Study Design-In vitro experimental study.

Sample Population-Twenty limbs from 6 cadavers (4 complete limb sets, 2 partial sets-total of 4 forelimb and 6 hindlimb pairs).

Methods-Two parallel 5.5 mm cortical (AO) screws were inserted in lag fashion in I randomly

allocated limb of a pair, and 2 parallel headless, tapered, variable-pitched, titanium compression screws (Acutrak-Plus®) were inserted in the contralateral limb. Constructs were tested in 3-point bending in a dorsopalmar (plantar) direction using a materials-testing machine at a loading rate of

5.83 mm/s. Maximal bending moment at failure and composite stiffness were calculated from data generated on load-displacement curves. Data were analyzed using a Friedman 2-way analysis of variance and Wilcoxon's signed-rank tests.

Results-No significant difference was detected for bending moment or stiffness values in proximal interphalangeal joint arthrodesis constructs using 2 parallel Acutrak-Plus® or AO screws for fix­ ation. Mean stiffness values were significantly different between forelimb and hindlimb constructs. Conclusions-Perfom1ance of 2 parallel Acutrak-Plus® screws was biomechanically comparable with 2 parallel AO 5.5mm cortical screws in in vitro pastern arthrodesis constructs.

Clinical Relevance-Acutrak-Plus® screws may provide an alternative means of fixation for prox­imal interphalangeal joint arthrodesis.

Surgical arthrodesis for the treatment of osteo­ arthrosis of the proximal intertarsal, distal inter­ tarsal and tarsometatarsal joints in 30 horses: A comparison of four different techniques
G. WYN-JONES and S. A. MAY
Division of Equine Studies with Farm Animal Surgery Department of Veterinary Clinical Science, University of Liverpool, Veterinary Field Station, Leahurst, Neston, South Wirral L64 7TE

Summary

Over a period of seven years, 30 horses were treated by surgical arthrodesis for lameness resulting from osteoarthrosis of the proximal intertarsal, distal lntertarsal and tarsometatarsal Joints (bone and occult spavin). Twenty-fhe horses were aff ec1ed in one hock only and five were affected bilaterally. Four different techniques for achieving arthrodesis were used. Fourteen out of 18 horses (78 per cent) with involvement of the distal intertarsal and tarsometatarsal joints only and six out of 11 horses (SS per cent) in which the proximal intertarsal joint was also involved became sound following surgery. The status of one other horse, with involvement of the pro,dmal inter­ tarsal joint, is not known.