Use of Computed Tomography in Standing Position to Identify Guidelines for Screw Insertion in the Distal Phalanx of Horses: An Ex Vivo Study

Objectives— To compare the precision of radiography and computed tomography (CT) preoperatively in the standing position for identification of guidelines for screw insertion in the distal phalanx, and to identify whether standing CT might improve operative time compared with preoperative radiographic planning.
Study Design— Experimental ex vivo study.
Animals— Cadaveric equine thoracic limb pairs (n=10).
Methods— Insertion of a 4.5 mm cortex screw in lag fashion into an intact distal phalanx was evaluated in 2 groups (n=10) of cadaveric equine thoracic limbs. In 1 group, the site, direction, and length of the implant were determined by radiography, and in the other group, by CT. Accuracy of screw placement was verified by specimen dissection. Outcomes were (1) absence of penetration of the articular surface, the solar surface, or the semilunar canal (2) appropriate length and direction of the screw. Surgical time was also measured.
Results— No screw penetrated the articular surface, the solar surface, or the semilunar canal in either group. CT was more accurate to identify guidelines for screw insertion (U=23.50, P =.049). With CT, surgical time (mean, 7.7 minutes) was significantly shorter (U=0.000, P =.000) than with radiography (mean, 12.7 minutes).
Conclusion— Standing CT can be used to accurately determine anatomic landmarks for screw insertion in lag fashion in sagittal fractures of the distal phalanx.
Clinical Relevance— This study has a clear clinical relevance for improved internal fixation of sagittal fractures of the distal phalanx.     

Comparison of Arthroscopy and Arthrotomy for Diagnosis of Medial Meniscal Pathology: An Ex Vivo Study

Objective— To evaluate the sensitivity and specificity of arthroscopy and arthrotomy for diagnosis of medial meniscal pathology and to evaluate the diagnostic value of medial meniscal probing. Study Design— Ex vivo study. Animals— Cadaveric canine stifle joints (n=30). Methods— Stifle joints were assigned to either a cranial cruciate ligament (CrCL) deficient or intact group. Within each stifle joint, no medial meniscal tear, a peripheral detachment, or 1 of 3 variants of vertical longitudinal tears of the medial meniscus were created. Each stifle joint had arthroscopy, craniomedial (CrMed), and caudomedial (CdMed) arthrotomy. Diagnoses were made by both observation and probing. Sensitivity, specificity, and correct classification rate (CCR) for diagnosing the state of the medial meniscus using both observation and probing with all diagnostic methods were calculated. Odds ratios were calculated to determine if probing increased diagnostic accuracy. Results— Arthroscopy with probing was the most sensitive and specific diagnostic method and had the highest CCR. For arthrotomy, CrMed was the most sensitive in CrCL‐deficient and CdMed the most sensitive in stable, CrCL‐intact stifle joints. For all methods, probing increased their diagnostic accuracy. Conclusions— Arthroscopy is the most accurate diagnostic method; however, probing the medial meniscus enhances the diagnostic accuracy of all methods. Clinical Relevance— Accurate diagnosis of medial meniscal pathology is ideally achieved by means of arthroscopy; however, if arthrotomy is chosen, CrMed should be selected in unstable and CdMed in stable stifle joints. Regardless, medial meniscal probing should be performed to increase diagnostic accuracy.     

Surgical Treatment of a Palmar Midsagittal Fracture of the Proximal Second Phalanx in a Horse

Second phalangeal fractures have been classified as either simple or multiple and have been managed in a variety of ways. The removal of small osteochondral fragments originating from the palmar midsagittal aspect of the proximal second phalanx is reported. This lesion has been described as a coincidental finding unrelated to lameness. Based on our clinical finding of lameness in this case and the response to an intraarticular injection of anesthetic, excision of the fragment was elected. However, the importance of confirming the significance of a radiographic lesion with local anesthesia prior to surgical intervention must be stressed.     

Lag Screw Fixation of a Patellar Fracture in a Horse

A vertical fracture involving the medial one-third of the patella of a yearling filly was successfully treated by lag screw fixation. Three months postoperatively the fracture was healed and the filly was clinically sound.     

Surgical Repair of a Comminuted Distal Femoral Fracture in a Dog

This case illustrates that good results may be achieved with fractured femur that was severely comminuted (i.e. a "Humpty Dumpty" fracture). The blood supply at the fracture site must be carefully preserved. The bony architecture must be reestablished with perfect reduction of the articular surfaces, preferably with interfragmentary compression between the bone fragments. These fragments are held in place with screws and Kirschner wires. Some of the screws and pins were left in place as the trauma incurred to retrieve them would have done more harm than good due to bony overgrowth.     

An Ex Vivo Biomechanical Study Comparing Strength Characteristics of a New Technique with the Three‐Loop Pulley for Equine Tenorrhaphy

Objective: To test single cycle to failure tensile strength characteristics of 6 suture material–pattern combinations in equine superficial digital flexor (SDF) tenorrhaphy, specifically to compare a 10‐strand modification of the Savage core suture technique with the 3‐loop pulley technique. Study Design: Ex vivo mechanical experiment comparing 3 different suture patterns with 2 different materials. Sample Population: Forelimb and hindlimb SDF tendons (n=48) harvested from adult Thoroughbred and Standardbred horses of mixed age and gender. Methods: Six suture material–pattern combinations were evaluated: (1) 10‐strand Savage, size 2 polydioxanone (PDS); (2) 10‐strand Savage, size 2 polyglactin 910 (PG910); (3) 10‐strand Savage, size 2 PDS with Lin‐locking epitenon suture, size 2–0 PDS; (4) 10‐strand Savage size 2 PG910 with Lin‐locking epitenon suture, size 2–0 PDS; (5) 3‐loop pulley, size 2 PDS; and (6) 3‐loop pulley, size 2 PG910. Maximum load at failure (N), gap at failure (mm), and mode of failure (suture breakage or pull through) were evaluated for each of the 6 suture material–pattern combinations and underwent statistical analysis to determine significance of differences and interactions of the measured data. Results: The 10‐strand Savage technique failed at a mean load of 872 N (804–939, 95% CI). The 10‐strand Savage with Lin‐locking failed at a significantly greater mean load of 998 N (930–1065, 95% CI). The 3‐loop pulley pattern failed with a mean load of 337 N (270–405, 95% CI). There were significant interactions between the technique and suture material used. Conclusion: The 10‐strand Savage technique for repair of transected cadaver SDF tendons has superior strength characteristics with or without the epitenon suture when compared to the 3‐loop pulley. Suture material and pattern interactions were observed with PG 910 conferring higher strength for the 10‐strand Savage whereas PDS did so for the 3‐loop pulley.     

Distal Humeral Salter Harris (Type II) Fracture Repair by an Ulnar Osteotomy Approach in a Horse

Objectives: To report repair of a comminuted distal humeral type II Salter–Harris fracture using an ulnar osteotomy approach and locking compression plates (LCP). Study Design: Case report. Animal: A 3‐month‐old Standardbred filly with a type II Salter–Harris fracture of the distal humerus. Methods: Radiographic and computed tomography examinations were performed to assist surgical planning. The distal humeral fracture was approached by an ulnar osteotomy and repaired using a 7‐hole broad LCP and screws inserted in lag fashion. The osteotomy was subsequently repaired using a 7‐hole narrow LCP. Results: The distal humeral fracture was successfully approached and stabilized by an ulnar osteotomy approach. At 6‐month follow‐up, the filly was ambulating comfortably with a normal cosmetic appearance. Conclusions: An ulnar osteotomy approach was readily performed and allowed for repair of a type II Salter–Harris fracture of the distal humerus. Clinical Relevance: The equine distal humerus can be accessed readily using an ulnar osteotomy approach. LCPs allow for repair of complicated fractures that have previously been associated with a grave prognosis.     

Suspensory Apparatus Prosthesis in the Horse Part 2: In Vivo Evaluation in a Suspensory Apparatus Disruption Model

The suspensory apparatus of one forelimb was surgically disrupted in six adult horses by transecting the distal sesamoidean ligaments. A double-braided prosthetic ligament made of aramid yarn was installed to support the flexor surface of the metacarpophalangeal joint. The prosthesis was routed through tunnels in the third metacarpal bone and proximal phalanx, and secured to bone with screws. Evaluation by radiography, synovial fluid analysis, cinematography, and dynamography was performed before surgery and at weeks 16 and 30. Supracondylar cortical lysis and periosteal proliferation were observed on postoperative radiographs. Synovitis and fragmentation of the prosthesis were apparent from synovial fluid evaluation. Weight bearing and metacarpophalangeal joint motion were decreased and loading was transferred in part to the opposite forelimb. Clinical lameness improved and weight bearing increased during the second half of the 30-week period. At necropsy, there was abrasion of the prosthesis and the articular surfaces in contact with the prosthesis. Diffuse granulomatous synovitis developed in response to aramid fiber fragments within the synovium.     

In Vitro Mechanical Evaluation of a Novel Pin–Sleeve System for External Fixation of Distal Limb Fractures in Horses: A Proof of Concept Study

Objective: To evaluate the efficacy of a novel pin–sleeve cast (PSC) system for external fixation of distal limb fractures in horses and to compare it with the transfixation pin cast (TPC) system. Study Design: Experimental. Sample Population: One bone substitute each was used for the TPC and PSC systems. The PSC was tested in 4 configurations characterized by different pin preloads. Methods: Specimens were loaded in axial compression in the elastic range. Variables compared statistically were: bone substitute axial displacement and axial strain measured above implants with strain gauges. Pin preload was correlated with the variables investigated. Load to failure and a fatigue tests supplemented the investigation. Results: The PSC configuration with the highest pin preload showed a significantly lower axial displacement compared with the TPC. No significant differences were observed between all other PSC configurations and the TPC. All PSC systems had a significant decrease in recorded strain compared with the TPC system. Pin axial preload inversely correlated with axial displacement but had no effect on axial strain. In the failure test, the PSC encountered plastic deformation earlier than the TPC. In the fatigue test, the PSC ran >200,000 cycles. Conclusions: Preliminary in vitro tests showed that the PSC system significantly reduced peri‐implant strain while concurrently having comparable axial displacement to the TPC system. Clinical Relevance: The PSC system has the potential to reduce the risk of pin loosening in horses.