Main topic: “A new approach to radial nerve palsy in cats”. Clinical Case Series Report

380533_338242309525656_1915103081_nby the Orthopedic department of “Dobro hrumvane!”veterinary clinics,

Sofia city, Bulgaria

  1. Introduction

The radial nerve palsy is a pathology that is rarely seen in dogs, in comparison to cats, where it is more commonly seen, especially in young stray cats. The most commonly observed clinical picture in such patients includes paralysis of the antebrachial portion of the limb, the carpus, the manus and fingers. According to our personal observations, in about 25% of these patients the elbow’s neuro-muscular apparatus is also involved, in a different degree.

The patients demonstrate an external rotation of the antebrachial area in relation to the portion of the limb above the elbow.

The carpus and manus possess an additional and permanent external rotation in relation to the antebrachium, which causes the patients to use the rostral portion of the their carpus for stepping and weight bearing, which in turn inducts the formation of a chronical traumatic inflammatory proliferative granuloma in this area. For about a 25-45 days period, an impossible to overcome carpal hyperfelexion develops, to the point where the joint can no longer be returned to its physiological position, due to the shortening of the flexor muscle-tendon apparatus (see video 1 with cat Sonia 39 days after the trauma at https://youtu.be/SZoXfp8tMJ0 ).

A few therapeutic approaches are being advised for this pathologic condition worldwide: total limb amputation; stem cell therapy (with still controversial results); standard pancarpal arthrodesis (note that very often it is very difficult to execute procedure in the state of this disease and is almost always accompanied by a nonsatisfactory limb function end result).

None of the upper mentioned approaches for treatment of radial nerve palsy in cats, while trying to avoid limb amputation, was producing satisfying results in the patients with this problem, operated by our team. This is the reason we decided to test and implement a new “Dobro hrumvane modified pancarpal arthrodesis” procedure for the operative treatment of feline radial nerve palsy.

  1. Report patients base

 

Up to this moment, this modified by our team procedure has been done in 111 patients. In the first 11 patients we tried different but very similar to each other versions of the modification, and after patient 12 up to patient 111 (meaning exactly 100 patients) we were performing always one same version of the technique.

In 87 of these patients a follow-up postoperative monitoring for over one year has been performed (in 9 of them an approximately 5 year follow up was achieved, in 33 patients the follow up period was approximately 4 years etc.), in 11 patients the follow up period was between 4 months and one year and in 2 patients the follow up period was less than 4 months. In four of the operated patients, pre- or postoperative clinically relevant paralysis of the elbow region was also observed. As was mentioned earlier, 25% of feline radial nerve palsy patients demonstrate this (according to our observations in 23% of the patients it is already observed in the preoperative period and in other 2%, it develops a few weeks after the surgical intervention, with the reasons for that still being unclear). It should be noted that the majority of owners of patients with elbow area involvement preferred amputation over the experimental procedure.

 

 

  1. Surgical technique

 

The standard pancarpal arthrodesis general guidelines are being followed, but with the following modifications:

  • Straight 11̊ inclination non locking hybrid pancarpal arthrodesis plate has been used  (produced by Medimetal or Mikromed, delivered by VetWest). The plate contouring should be modified before the surgery and the inclination should become 21-22̊. Twisting of the distal portion of the plate internally in relation to the proximal portion of the plate is not recommended! For the fixation to the metacarpus 1.5 mm non locking screws were used (produced by Mikromed, delivered by VetWest) and for the fixation to the radius 2.0 mm non locking screws were used (produced by Mikromed, delivered by VetWest);
  • The proximal (os carpi radiale et ulnare) and distal carpal bones are being completely removed, this being done with extreme caution not the traumatize the adjacent magistral structures (especially blood vessels), which are located on the palmar surface;
  • The proximal ends of the metacarpal bones are being separated from one another;
  • The fixation of the plate to the dorsal surface of the third metacarpal bone is achieved the same way as in the standard technique, using 1.5 mm thick and 6 mm long screws, but the fixation to the radius is not applied on its dorsal, but on its medial/mediocaudal edge/surface, using 2.0 mm screws. The screw hole on the plate which is intended for os carpi radiale (note that this bone is actually removed  in the modified technique) is used for an additional 2.0 mm screw, placed in the distal radius. In other words, the whole metacarpal portion of the limb is being internally rotated around 85-95° (for the purpose of that an almost full blunt and careful separation of all soft tissues, including the magistral vessels and nerves in the distance between the carpus and the middle portion of the metacarpal bones, should be performed). After plating of the third metacarpal plate with four 1.5 mm non locking screws in neutral position the third metacarpal bone is being compressed to the radial distal This compression is easily achieved with the first screw, placed in the radius (not dorsal but medial/mediocaudal radial edge/surface – see below Xray picture Standard) thanks to the DC wholes of the plate types mentioned upper above. This screw is being inserted in the second 2.0 mm screw whole in distal to proximal direction, meaning the third plate hole in relation to the whole plate in proximal to distal direction. After that, 4 neutrally (not in  compression mode) placed screws are applied to radial bone in the following order: the most distal hole, the most proximal hole, the second hole in proximal to distal direction, the third hole in proximal to distal direction. It is recommended that at least two of the screws in the distal radius engage the distal ulna too, so the distal portions of the two bones could eventually be pulled together – the screws could be numbers one and two or four and five from proximal to distal, this possibility could be estimated only intraoperativelly;
    pic1

    POST-OP STANDARD X-RAY PICTURE AFTER PANCARPAL ARTHRODESIS “DOBRO HRUMVANE”

    • With this technique it is easy and recommendable to use a significant amount of autograft material – recommendable due to the large gap that is being created. This autograft is readily available, considering the amount of bone that is being removed in the previous stages of the surgical technique;
    • The final stage of the surgery includes almost full blunt separation of the skin from the underlying soft tissues in the designated area, along with skin plastic traction modification, which is intended to place the fifth finger in a more medio-cranial position. The skin sutures and respectively the skin incision should be placed in a position that is not exactly above the plate (eventually they plate and incision could be placed in a cross manner, but should not be on top of each other for their whole lenght). It is not necessary to perform tenodesis of the digital extensors or excision of some skin on the dorsal carpal area in orther to pull the fingers in extension. It shoud be noted that the upper mentioned skin traction used to “pull” the fifth finger in a more dorsal and medial direction (meaning that the fifth finger is placed adjasent to the dorsolateral, not solely lateral, surface of the fourth finger, under subtle tension that will not allow overlapping of the fifth finger) is extremely important because in some of the first patients, which underwent the still not perfected procedure, weeks to months after the surgery pressure necrosis developped in the fifth finger, which required further revison plastic surgeries.
    • In patients that have a very wild temper and where it is not possible to achieve two week long cage rest, postoperative splint could be placed. If this is done, additional amount of cotton could be used to help achieve the upper mentioned mediocranial position of the fifth metacarpus and finger;
    • NEO K-9 clinical formula is prescribed for a month and a two week long cage rest is done in more calm patients.

     

     

    1. C) Results – the last 100 cats (No 12 … No 111 made with identical technique) :

     

    C1) 96 patients that did not have (according to our clinical opinion) involvement of the elbow region pre- or postoperatively:

    – 95 patients with good limb geometry in stance and during walking, active involvement of the limb during walks and playing, owners completely content with the results 4 months up to 5 years after the surgery. 89 of these 95 patients had no postoperative complicatioons; 2 patients developed moderate postoperative infection that was easily treated; 2 patients demonstrated delayed healing of the surgical incision in the area above the plate (it took more than 5 weeks in both patients); 2 patients had delayed bone union, that took around 5 months to be completed;

    – 1 patient demonstrated unsatisfactory to this point level of weigt bearing and limb usage during walk and play. It is understandable that the owner of this patient is not completely content with the results, but is unfortunately refusing implant removal and further diagnostic procedures;

    – No cases with implant loosening, intra- or postoperative fracture, postoperative necrosis etc.;

     

    C2) 4 patients with clinically relevant pre- or postoperative involvement and paralysis of the motor unit of the elbow joint:

     

    1 patient without preoperative elbow problem, developed such around a month after the surgical intervetion and the problem was accompanied by the development of an additional low grade external rotation of the antebrachium in relation to the limb portion above the elbow. The main problem was presented by progressive loss of support of the ebow joint in extension during stance, which lead to the inability of the limb to support the body during weight bearing. The problem was resolved after a two week long active rehabilitation and machine physiotherapy and application of a light splint, which is suporrting (but not blocking) the elbow.

     

    – 1 patient (cat named Trun) with preoperative paralysis of the elbow joint, but accompanied by almost complete ankylosis of the elbow joint (only 15% of the normal range of motion was preserved, especially the extension was blocked) – see below the post-op pictures of cat Trun

    pic 2

    cat Trun

    pic 3

    cat Trun

    Although there was a serious accompanying problem, months after the surgery the owners are completely satisfied with the result. The patient is using the limb with no limitations during play, almost no limitations while running and with some limitations while walking – that last limitation is probably due to the constant flexed position of the elbow, which is exceeding the normal flexion angle of an elbow joint during walk, thus the animal is placing the shoulder of the affected limb under the level of the shoulder of the unaffected limb, during weight bearing (see video with cat Trun approx 3 months post-op at https://youtu.be/N9scMppZeyo ). The owners do not report signs of pain. Even though it is not right to make conclusions only on the basis of a single patient, this case gives us hope that patients with radial nerve palsy in combination with complete or partial elbow joint ankylosis have the chance to avoid amputation of the limb.

     

    – 1 patient with partial preoperative paralysis of the elbow joint which became more severe (around  50%) month after the surgery: the bones in the arthrodesis region achieved complete healing, but the elbow joint loses support during weight bearing,  thus the animal is placing the shoulder of the affected limb under the level of the shoulder of the unaffected limb, during weight bearing. Due to this the ptient is weight bearing the limb not on its pads, but rather on the carpal palmar angle surface. Because of that a chronic nonhealing skin lesion developed in this area over the time, which is intermitently bleeding. Up to this point, the owners are content with the result and do not wish to start rehabilitation or agree to a revision surgery, but for our team this result is unsatisfactory and it requires additional surgical and/or physiotrepautical intervention;

     

    – 1 patient (Doxy) wtihout preoperative involvement and paralysis of the elbow, which developed a progressive clinically relevant paralysis of the elbow a few weeks after surgery. This led not only to loss of support of the elbow joint during weight bearing, but also to constant progressing additional rotation of the antebrachium in relation to the humeral area.

    pic 4

    X-RAY PICTURES DOXY

    pic 6

    X-RAY PICTURES DOXY

    This rotation made the patient bear weight on the lateral surface of the carpal angle, developing a skin lesion there. This postoperative elbow joint paralysis did not resolve after a rehabilitation course. In order to correct the problem an elbow arthrodesis was performed, but not in a standard way. A “double-modified” elbow arthrodesis was performed: the boomerang plate produced by Mikromed and supplied by VetWest was placed on the lateral surface instead of the medial. Also, the antebrachial region was rotated 18 degrees internally, in relation to the humerus. We recommend very torough preoperative preparation: the execution of the technique is quite challenging, because the compression must be maintained and in the same time the “locking” of the anconeal process in the humeral fossa must be overcome, along with the congruency of the other ulnar structures and their corresponding radial structures – see below post-op X-ray pictures of cat Doxy after the second surgery, the elbow modified arthrodesis:

    It can be seen that the plating is on the lateral surface of the radius distally and on the laterocranial surface of the humerus proximally.

    Only a few hours after the surgery, the patient demonstrated excellent, pain free limb usage, with very good limb geometry and lack of difference in the level of the two shoulder joints during weight bearing. In the following days the patient started using the limb for playing too. At this point, 3-4 months after surgery, the patient is demonstrating completely satifying results (see video with cat Doxy approx 4 months post-op at https://youtu.be/X_rFEgrZink ). There are no signs of malunion, infection or other types of complications. The muscle mass in the shoulder area of the operated limb is similar to that of the non operated limb. Even if it is based just on one patient, the result of this case gives us some hope for surgical resolution for patients with modified or standard carpal arthrodesis, which have an acompanying or later develop severe elbow pathology of nonakylotic kind, as we know that the combination of carpal and elbow arthrodesis is not recommended in the known sources. For this patient especially we have an additional recommendation:

    1) The first recommendation that is applied to all 111 operated patients – considering that it is a patient with a paralysed limb it should live on a non- smooth surface (but also not on an abrasive one). On a slippery surface patients with Dobro hrumvane arthrodesis step with mild slipping which combined with the lack of sensitivity could cause in longer period skin lesion (see Video 2 with cat Zhivka approx 5 weeks post-op at https://youtu.be/hKKjmO9yWdI ).

    2) Additional recommendation especially for Doxy: the patient has two joints that underwent arthodesis, which means that a stress point is being created between the two plates, which in turn creates a significant risk for further fractures. This risk is further amplified by the fact that the arthrodesis procedures are reducing the shock absorbing function of the joints. Considering all of the mentioned above, the patient should live in an enviornment that lacks the risk of creation of serious vertical vector forces (such as jumping to or from high places). It should be noted that Doxy did exactly that, many times after surgery and no problem occured, but it is still highly not recommended.

     

    1. Conclusion

     

    The 100 clinical cases, with patients that underwent a similar modified pancarpal Dobro hrumvane arthrodesis procedure for the treatment of feline radial nerve palsy demonstrate a constant and satisfying result with very good return to function of the limb, pain free, with no discomfort. No following complications, including long-term ones are being observed and there is a very high level of owner satisfaction. We recommend this surgical technique and we would be glad to recieve feedback afer the completion of the procedure, either in the algorithm recommended by us, or with any additional modifications.

    pic 7

    Hari

    Even when the rotation of the metacarpal area in comparison to the antebrachial area is not 85-95 degrees the patients use the leg and the owners are satisfied but the leg geometry is in our opinion not good looking. Cat number 11, the last before the standartized 100 patients chain, named Hari is such a case, the rotation was 78-80 %, the operation was made approximately 5 years ago. As you can see at the videos made 4 years post-op the patient uses the left operated leg even during acrobatic jumping (see below picture Hari)

    and active playing (see video Hari 4 years after surgery at https://youtu.be/SfhzUtLr9ig ).

    1. E) Post scriptum

    A few years ago we presented the technique and its results, based on a few dozens of cases, on a VOG\BAVOT event. Ever since, a few colleagues from the Balkan region have sent us feedback with very encouraging results, after using the technique. One of them was our inconsolable friend, colleague and inspirator, D-r V. Vasilev, whose memmory and collosal contribution to the development of the veterinary meidicine in Bulgaria we would like to honor in the end of this report.

     

     

              Sofia                                      The Orthopedic department of

       March 2019                            “Dobro hrumvane!” veterinary clinics

     

Transplantation of ipsilateral canine ulna as a vascularized bone graft for treatment of distal radial osteosarcoma

12959354_10153530931267960_1853416198_o-200x300

Dr. Vladislav Zlatinov,

Corresponding author :

Dr. Vladislav Zlatinov,

Central Veterinary Clinic

Chavdar Mutafov str, 25 B, Sofia, Bulgaria

E-mail: zlatinov_vet@yahoo.com

 

 

Abstract

 

This case report describes the successful use of a vascularized cortical autograft from the ipsilateral ulna in limb-sparing surgery for the treatment of distal radial osteosarcoma. A pancarpal arthrodesis with two orthogonal plates was performed to stabilize the site. No implant failure and local tumor recurrence were observed in the 6 months post operative period. Excellent limb function was achieved within 6 weeks after surgery; no external support (coaptation) were used during the post operative period. Excellent perceived quality recovery, was reported by the dog’s owners, compared to their preliminary outcome expectations.

 

Introduction

 

Osteosarcoma (OSA) is the most common primary bone tumor in dogs, most commonly affecting the distal radius. Current treatment protocols-Fig.1 are based on a combination of surgery (limb amputation or limb sparing surgery) and adjuvant chemotherapy. Palliative therapies like- Stereotactic radiation or Percutaneous

Fig.1

Fig.1 Osteosracoma treatment algorithm

Cementoplasty therapy are rarely applied with limited success 1,2.

 

 

 

 

 

 

 

 

 

 

 

Recently, numerous publications suggest that the Limb-sparing surgery is a viable alternative to limb amputation in selected cases, especially indicated if there is pre-existing orthopedic or neurological disease or if owners are resistant to limb amputation 3,4,5,6.

 

 

Limb- sparing consists of removing the segment of bone involving the primary tumor and using internal or external fixation to the remaining bones with or without segmental bone replacement, resulting in a salvaged functional limb 7. Limb- salvage procedures

have been described in the distal aspect of the radius, proximal humerus, distal tibia, and proximal femur in dogs with OSA, but the salvage surgery of the distal aspect of the radius has produced the most favorable results. This is mainly because pancarpal arthrodesis is well tolerated by dogs, not like fusion of other joints. Importantly – the prognosis for survival is the same with amputation or limb- sparing, unless an infection is present, in which case the average survival is prolonged.

 

Candidates for limb sparing

 

Good surgical candidates are dogs with OSA confined to the bone, with minimal extension into adjacent soft tis­sue and involving less than 50% of the bone length. The extent of bone involvement is most accurately determined by using computed tomog­raphy and is overestimated by radiography, nuclear scintigraphy, and magnetic resonance imaging 8. Pathologic fracture is a relative contraindication for limb-sparing because of tumor seeding into adjacent soft tissue, although the risk of local tumor recurrence can be re­duced by use of preoperative chemo­therapy or radiation therapy.

 

 

Limb sparing techniques

 

Historically, the most commonly performed limb sparing technique for the distal radial site involved the use of an allograft (donor from an individual of the same species) to replace the bone defect created by segmental bone excision 9- Fig.2. Although the limb function is good to excellent in about 80% of dogs with the allograft technique, the complication rate is substantial. The most common complications include infection, implant related problems, and local recurrence. Infection rate is reported to be up to 60%, implant failure in up to 50% as well. Even more, there are practicality issues for the regular application of the allograft technique- time consuming and costly maintenance of a bone bank. Recently,  there is a new alternative for graft purchasing from a commercial source on a case by case basis.

Fig.2

Fig.2 Allograft limbs spring surgery

 

It’s not surprising that alternative limb-sparing methods are being investigated. Reported grafting techniques include pasteurized/ irradiated autografts, endoprosthesis, vascularized ulnar transposition graft (roll-over technqique), free microvascular ulnar autograft.

 

Nevertheless the technical evolution of the available techniques, all of them are still often associated with a high complication rate including infection, construct failure, and tumor recurrence. The longitudinal or transverse bone transport osteogenesis has the advantages to lower the aforementioned complications but still have limitation for routine implementation in the practice 10, 11.

The advantages and disadvantages of the recent innovative techniques are shortly summarized below.

 

Fig.3

Fig.3 Endoprosthesis limb salvage procedure

The most prominent advantage of the endoprosthesis limb salvage (Fig.3) is the simplicity compared to the other grafting techniques; consequently it is time-saving. Decreasing the surgery time may suggest lower infection ration.  Unfortunately this was not proved by the clinical experience with the currently commercially available endoprosthesis.

 

 

A recent study 4, comparing the results of  Cortical Allograft and Endoprosthesis techniques, suggested  surgical infection of 60 and 55% of the cases, respectively. The use of a large volume of implants and foreign material has been proposed as a cause. More over in the same study, long term implant failure occurred in 40% of the treated dogs.

A positive remark in the paper is the good (subjectively) limb function, reported in the stable phases or in non-complicated cases.

 

Fig.4

Fig.4 Ulnar roll-over salvage technique

A more biologic friendly technique- ulnar roll-over – Fig.4 was resently reported with good results, despite limb shortening of up to 24 % 3,12,13. The distal ulna is osteotomized, rolled into the radial defect, and secured with a bone plate and screws. With this technique the preservation of the caudal interosseous artery and vein and a cuff of the deep digital flexor, abductor pollicis longus, and pronator quadratus muscles are important for maintaining viability of the transplanted ulna.

 

 

Theoretically, using a vascularized bone graft could reduce the gross incidence of complications compared to an allografts or endoprothesis. Vascularized bone is more resistant to infections, to the extent that vascularized cortical autografts have been used to treat osteomyelitis. Also the use of a viable graft may preserve biomechanical properties over allografts. Whereas the allograft may resorb and become weaker over time, the ulnar graft may maintain its physical properties or even hypertrophy and healing with the host bones.

However, the statistics reports are controversial, with no clear proof for substantially better outcomes. One study shows no statistically different infection (45%) and implant failure (55%) ratio. Probably the presence of a viable graft does not address all other factors predisposing to infection (poor soft tissue coverage, immunosuppression from neoplasia and chemotherapy, and use of orthopedic implants). The other complication problem- implant failure, sounds as  a surgeon’s skills dependent issue. For example one of the major complication in the mentioned study has been fracture of the remaining radius in cases of great length resection (>57%), which could be just consequence of suboptimal plate length or screws number and distribution.

Importantly, the roll-over technique demands sufficient length of the distal ulna to be preserved, but local recurrence was not increased compared to other limb- sparing techniques.

Microvascular anastomosed bone transfer was used in the presented case. This is a routine procedure in the limb sparing surgeries in human patient, but rarely applied technique in veterinary medicine, nevertheless, the vascular supply of the distal ulna has been , studied, described and successfully used experimentally and clinically 14,15.

In this technique, a more substantial middiaphysis segment of the ipsilateral ulna, with its source artery and vein (the common interosseous) is harvested and transpositioned, with a blood supply restored by vascular anastomosis to a neighboring artery and vein, once the graft is in its new position. The surgical technique is described further in the text. The concept is the same as the ulnar roll-over but, with the advantages of stronger cortical ulnar graft used, more mobile graft and  a chance for full distal ulnar resection. The disadvantages of this procedure are the need for a specially trained and equipped microvascular team and the prolonged surgical time.

Longitudinal bone transport osteogenesis

 

Fig.5

Fig.5 Longitudinal bone transport osteogenesis

This is a specific application of distraction osteogenesis, which has been used successfully in dogs for replacement of large segmental defects of the distal aspect of the radius and tibia after tumor resection. This is a process whereby healthy, detached bone segment is sequentially moved across an adjacent segmental osseous defect forming new regenerate bone in the distraction gap -Fig.5.The regenerate bone is highly vascular and resistant to infection.

The results following the procedure have been very encouraging, with good orthopedic function and no reported infections. Disadvantages of the bone transport osteogenesis procedure is the significant amount of time required to fill the defect after tumor removal (up to 7 months). This often leads to owner compliance issues (distracting the apparatus two to four times per day), also pin-tract drainage and loosening, difficulty in docking the intercalary bone onto the radial carpal bone.

Fig.6

Fig.6 Transverse Ulnar Bone Transport Osteogenesis

A recent modification –Transverse Ulnar Bone Transport Osteogenesis, has been reported 16- Fig.6. The technique substantially decrease distraction times. In one case report,  distraction of the ulnar transport segment across the 84 mm longitudinal segmental radial defect, was completed in 23 days.

 

 

 

Case report

 

 

A 9-year-old female Rottweiler dog (43 kg) was referred to our practice with a 3- weeks history of left forelimb lameness with an gradual onset and an unknown origin. The dog was been previously prescribed NSAIDs with temporary effect. During our examination we found weight-bearing lameness II/V. Physical and orthopedic examination revealed distal radial swelling on the left forelimb, with pain on extension of the carpal joint.

 

Fig.7

Fig.7 Orthogonal limb radiograph

Orthogonal radiographs were achieved, revealing vast osteolytic (relatively smooth margins) area in the  distal radius, with no apparent lesions in the distal ulna- Fig.7

 

 

Based on the history, signalment, lesion location, and radiographic findings, a primary bone tumor was suspected.

Fig.8

Fig.8 Thoracic X ray

No abnormalities were detected on preoperative 3-view thoracic radiographs, abdominal ultrasound, echocardiography, and blood tests- Fig.8. The Alkaline Phosphatase (AP) value was 195 U/L- in the upper limit but still within the reference range for the breed.

Treatment options were discussed with the owners:

 

-conservative palliative treatment

-amputation and chemotherapy

-limb-sparing surgery in conjunction with chemotherapy;

 

The owners chose the last  course of treatment but insisted on preoperative histologic confirmation of the suspected diagnosis.

 

Fig.9

Fig.9 Pathological fracture of the cranio-distal cortex

After short anesthesia and minimal invasive approach, tissue biopsy sample was retrieved and send for analysis. Ten day later the the suspicious of osteosarcoma neoplasia was confirmed. The histologist comments were: moderately aggressive OSA with low mitotic figures. Meanwhile the dog showed acute lameness deterioration, related to a pathological fracture of the cranio-distal cortex of the radius, following the biopsy procedure- Fig.9.

 

A limb sparing procedure (roll-over vs. free vascularized) grafting was planned.

 

Twenty minutes before the skin incision high segmental epidural analgesia wad accomplished at the level of T11, infusing 2 ml of 0,25 % Levobupivacian solution and positioning the patient in left lateral recumbency for 10 minutes- Fig. 10.

 

 

Fig.10

Fig.10 Segmental epidural analgesia

Fig.11

Fig.11 Sternal recumbency

 

 

 

 

 

 

 

For the surgical intervention, the dog was positioned in sternal recumbency- Fig 11. , facilitating  a dorsal approach to the radius and carpus. Careful tissue examination was done during the sharp dissection of  the distal soft tissues. Caudally, the tumor was closely attached to the distal ulna. Thus, the tumor was not dissected caudally to avoid contamination. A decision for a more extending distal ulnar resection was made. This prevented the option for roll-over technique more advanced free vascularized transfer was prepared.

The extensor carpi radialis muscle was transected proximal and distal to the tumor; the common and lateral digital extensor tendons were spared. An oscillating saw was used in both radial and ulnar osteotomies. The level of the transverse osteotomy of the radius, 2 cm proximal to the tumor, was determined on radiographs and confirmed appropriately intraoperatively. The ulna was osteotomized at lower level, just over the overlapping zone with the radius. The radius was disarticulated at the antebrachiocarpal joint and the tumor removed en bloc with the distal ulna. The length of the resected radial segment was 10 cm, including the 2-cm free margins (this represented 45% of the total radial length). The whole radio-ulnar segment was stored in 10 % formalin solution for later histologic analysis-Fig.12 and 13

 

Fig.12

Fig.12

Fig.13

Fig.13

 

 

 

 

 

After tumor removal the limb sparing was continued with cartilage debridement from the carpal and metacarpal bones , accomplished by using a speed burr drill; several penetrating drill holes were created in dorsal surface of the radial carpal bone.

The resected radial bone segment was measured and a second ulnar osteotomy performed proximally using a separate blade to match the length of removed radial bone minus 1,5 cm. The proximal ulnar osteotomy was performed above the level of the radial osteotomy while identifying and carefully dissecting the caudal interosseous artery and vein.The last were a-traumatically clamped and transected as proximal as possible, preserving as much as possible of the vessel length.The muscle attachments of the abductor pollicis longus, ulnar head of the deep digital flexor, and pronator quadratus were kept intact onto the periosteum of the distal aspect of the ulna.

The ulnar graft was transposed into the radial defect and the proximal end of the common interosseal artery (<2  mm) was anastomosed to a distal branch of the median artery. The anastomosis was accomplished with the use of magnification (10x) with surgical microscope and fine jewelers forceps- Fig.14 and 15. General principles of end-to-end vascular anastomosis were followed- atraumatic handling, distance of 0,5- 1 mm from the vascular wound’s edge, the regular suture distance, etc. Five interrupted sutures (8-0 nylon) were used to seal the anastomosis. The total ischemic time of the bone graft was about 60 minutes.

Fig.14

Fig.14 Microscope- assisted arterial anastomosis

Fig.15

Fig.15

 

 

 

 

 

 

 

 

The microanastomosis success was confirmed by identification of a active blood flow present in the graft’s tissues and the distal end of the interosseal artery (video 1 ).  The corresponding vein was not anastomosed, but its end was left free in the surrounding soft tissues. The distal artery ending was ligated.

 

 

After the anastomosis, the procedure was finished by stabilization of the bone graft by long plate, engaging from the distal metacarpal bones to the proximal radius, on the cranio-dorsal surface. We used hybrid 4,5 mm plate (Mikromed, human series) allowing fixation with 4,5 mm screw proximally, 3,5 mm in the middle area (free graft) and divergent 2,7 mm screws in the III and IV metacarpal bones. A second orthogonal plate 3,5 mm reconstructive locking (Mikromed) was applied laterally, fixating the proximal radius to the fifth metacarpal bone- Fig.16 and 17. Copious cancellous bone graft (from proximal humerus) was retrieved and stacked at the level of all osteotomy gaps.

Fig.16

Fig.16

Fig.17

Fig.17

 

 

 

 

 

 

 

 

 

 

After copious wound lavage and before closing of the surgical wound, the implants were covered by Gentamycin impreganted bovine collagen sponges (Gentacoll- resorb). The goal of the last was infection prevention. A soaker catheter was also inserted along the full length of the surgical wound. Subcutaneous tissue and skin were closed routinely. After skin suturing, the leg was bandaged  with modified Robert -Jones bandage for the next 12 hours. The soaker catheter was attached to elastomeric pump, delivering 1 % Lidocain solution – 5 ml/h, for the next 3 days.

 

 

Post operative care

 

 

Postoperative analgesia consisted of: local Lidocain flash block delivery by the elastomeric pump (36 h) , Butorphanol  (0.3 mg/kg, every 6 h, i.v.) and meloxicam (0.1 mg/kg /24h ,s.c.).

 

Fig.18

Fig.18

Cryotherapy (frizzed towels compresses) was applied every 4 hours for the  next 48 h- Fig. 18

 

Cephazolin (20 mg/kg/8 h, i.v.) was applied for 3 days post op.

 

 

On the third post operative day -the dog was discharged, with oral Cimalgex (Cimicoxib, 2 mg/kg/day) for 14 days. Oral amoxicilin clavulonic acid  (12,5 mg/kg/12h) was administered for 2 weeks and exercise was restricted to short walks on a leash for 12 weeks. The dog was re-examined regularly- every 14 days, including the visits for the chemotherapy sessions.

 

Chemotherapy protocol

 

Fig.19

Fig.19

The histopathological diagnosis of the excised bone confirmed a grade II fibroblastic osteosarcoma (OSA)– Fig. 19. Surgical resection was considered complete with no evidence of neoplasia at joint compartment.

 

Fig.20

Fig.20 Carboplatin

A single agent protocol -carboplatin (300 mg/m2)- Fig. 20,  was planned and applied every 3 wk for a total of 5 treatments. The first treatment was started 2 weeks after surgery. A CBC was taken 2 weeks after and just before each carboplatin administration; serum biochemistry was performed every 2 months. There was no evidence of gastrointestinal upset, renal failure or  myelosupression after chemotherapy. The AP levels were always in the reference range.

 

 

 

 

Clinical recovery and Follow up

 

 

Lameness progressively improved from toe-touching (one day after surgery) to full weight-bearing with only slightl visible lameness- 6 weeks post op. No external coaptation was applied during the recovery period- Fig.21, Video 2- 3.

 

 

 

Fig.21

Fig.21 Three weeks post op

Fig.22

Fig.22 Six months post op

Fig.23

Fig.23 After lateral plate removal

 

 

 

 

 

 

 

 

 

 

 

 

 

Six months post op the limb function was appreciated as excellent, without any significant changes on limb palpation- Fig.22. Video 4. Orthogonal radiographs were taken, showing proximal bone fusion; distally the bone was superimposed by the lateral plate. No signs of construct failure were observed. A decision for dynamisation was made and the lateral plate was removed, revealing radiographically the bony structure under it. It showed good bone density and excellent graft fusion (primary), proximally and distally. Further segment hypertrophy is expected by the increased load sharing.

 

 

 

 

 

CONCLUSIONS

 

The limb sparing surgery could be a viable option for treating distal radial OSA in properly selected cases. With the innovative alternatives, the widely accepted approach to canine OSA – limb amputation treatment, should not be applied as “default treatment” in each case.  Case to case individual approach may provide the pets and their owners more fare attitude. Excellent functional results of the limb may be achieved by a complex (but single stage) surgical segment resection and appropriate bone reconstruction and rigid fixation. The use of free vascularized bone graft is a manageable option and an alternative to ulnar-roll over in cases of distal ulnar tumor engagement or vast radial segments resection, where solid vascular bone grafting is demanded.IMG_6122

Total hip replacement after unsuccessful femoral head and neck resection in large mix breed dog

12959354_10153530931267960_1853416198_o

Dr. Vladislav Zlatinov

Corresponding author :

Dr. Vladislav Zlatinov,
Central Veterinary Clinic
Chavdar Mutafov str, 25 B, Sofia, Bulgaria
E-mail: zlatinov_vet@yahoo.com

Key words : Total hip replacement, FHNO revision, Biomedtrix universal hip system, BFX, CFX

 

Abstract

 

This a case report of successful revision of femoral head and neck ostectomy (FHNO) with hybrid BioMedtrix (Boonton, NJ) total hip replacement (THR) system, in a 7 years old mix dog. The revision indications in the case were chronic pain and functional impairment after previous excision arthroplasty for severe coxo-femoral arthritis. The weight of the patient (43kg), incomplete resection of the femoral neck and concomitant orthopaedic condition (elbow osteoarthritis) could had been contributing factors for the FHNO bad outcome. A preoperative computer tomographic (CT) study was used for underlaying cause exploration and planning the replacement arthroplasty. The time window between the two surgeries was unusually long- three years. This had caused serious morphological alterations and made the surgery of upmost technical difficulty. Nevertheless, the revision of FHNE to THR produced marked clinical improvement and return to normal activity within 3 months after surgery.

Introduction

 

THR is a salvage procedure involving replacement of a diseased pelvic acetabulum and femoral head with implants. Common diseases which necessities this advanced bionic surgery are osteoarthritis, secondary to hip dysplasia or trauma, aseptic femoral head necrosis, acute or chronic hip luxation, failed FHNO, irreparable acetabular or femoral head fracture.
Actually, the canine THR became commercially available since 1974 (Hoefle) and huge advancements in canine and feline THR have been made in the past 30 years. At the present, two cementless commercial systems are most popular, and several other under development1.
The Zurich Cementless Hip Prosthesis (Kyon, Switzerland) provides immediate fixation of the acetabular cup by a press-fit insertion (plus option for screw fixation); Locking screws are used for immediate fixation of the femoral stem, and on growth of bone provides long-term stability.
The BioMedtrix biologic fixation system (BFX) is a modular, press-fit bone ingrowth system with an unsecured acetabular component that provides the advantage of size compatibility with the components of the BioMedtrix cemented THR system (CFX). The advantages of application hybrid THR are discussed further in the case report.
Implants design and procedures in canine THR have been well reviewed in the literature. There are several studies reporting the functional outcomes and complications.2,3 Over- all excellent clinical results and reasonable (2-5%) major complications occurrence are reported by the experienced surgeons in the field.
Never mind the specific implant system used, the THR surgery should achieving the ultimate goal of relieving pain and improve the patient’s quality of life by returning normal limb function. Optimally, the functional effect and the integrity of the prosthesis should last for a lifetime. Serious complications- that could be met in the procedure should be avoided by precise surgery planning and perfect aseptic and surgical technique.
Femoral head and neck ostectomy (FHNO) is alternative low- cost salvage procedure. It intend to eliminate bone-to-bone contact of the diseased acetabulum and femoral head, through the formation of a pseudoarhrosis composed of non-painful fibrous connective tissue.
Published reports about outcome results after FHNO have been controversial. These ones based on gross veterinarian observations or client questionnaires, show encouraging improvement in clinical signs for the majority of dogs.
The more objective gait analysis data (available only recently4,5,6,7) didn’t reveal so optimistic results. Not ideal outcome in function was most evident in studies that did not rely only on owner satisfaction. Common residual dysfunctions after FHNO include: persistent lameness, restricted hip ROM , limb shortening, decreased stifle and hock angulation and muscle atrophy. The maximum functional recovery from the procedure may take up to 8 months6,7,8. Logically, the functional outcome of FHNO is affected by surgical technique, severeness of the disease, age, post op physical therapy and body weight 9. Several clinical trials suggest lack of constant results in dogs heavier than 18 kg.10,11,12 . The cause of the suboptimal outcome in larger dogs is still controversial. Some studies blame the bone-to-bone contact from inadequate excision or postoperative bone proliferation13,14; Others suggest that the bone contact is commonly found after FHNO and do not explain the different clinical outcomes15,16.
In cases of unacceptable pain relief, following FHNO, a revision osteotomy could be contemplated to correct a residual bone-to-bone contact, if present. A more aggressive ostectomy (including trochanter minor) or usage of muscle flaps “slings” modifications could be used to improve the outcome, again with unpredictable outcomes12,17. Another viable option could be conversion to THR18,19,20 . Nevertheless, revisions to THR were reported to yield good and pain-free function (Gofton, 1982; Liska et al. 2010, Fitzpatrick et al. 2012) many obstacles lay in front of successful procedure. The presence of unstructured fibrous tissue and altered anatomy at the surgery site complicates the surgery, and manipulation of a previous surgical site increases the risk of infection. After an excision, the acetabulum fills in with bone and the proximal femur remodels with bone resorption at the excision surface and sclerotic bone production in the medial proximal endoosteal surface. Complications are more likely after revision of FHNO, so dogs that are initially better candidates for a THR, should not be offered excision as an interim procedure.

 

Case report

A 7 years old female mix breed dog (43kg) was presented for consultation because of chronic left hind leg lameness. A femoral head and neck excision was accomplished 3 years ago, but the patient never show adequate pain-free recovery afterwards, despite persistent usage of anti-inflammatory medications.

 

Disease history

The patient had a history of previous surgeries (Fig.1-2)- left hip luxation was treated by toggle-pin reduction technique, five years ago. At the same traumatic incident, right intra articular ulnar fracture was diagnosed and osteosynthesis with neutralisation plate was applied. Despite the successful healing, degenerative joint changes developed gradually in the elbow afterwards.rtindex1

In the previously luxated left hip, progression of severe degenerative changes and clinical deterioration towards severe disabling lameness were demonstrated after the treatment. This why, FHNO was accomplished 18 months after the primary trauma (Fig.3). Radiographic signs of osteoarthritis progression were noticed also in the opposite, right hip joint. The primary cause was hip dysplasia, but no painful clinical consequences were confirmed.ij

 

Clinical examination

At the clinical exam we found a moderate (II/IV) left hind leg lameness. (video1). At manipulation the hip demonstrated restricted ROM, with obvious pain and crepitation feeling in extension.We found considerable limb muscle atrophy. The opposite hip also had decreased ROM but no pain was elicited through extension.

A CT imaging was used for better evaluation of the FHNO failure (Video 2). Our clinical and imaging interpretation was- residual bone-to-bone contact, caused by suboptimal FHNO and caudal- distal “under-excised” femoral neck.

 

 

Dorsal displacement of the femur could have exaggerated the residual contact. Schiatic nerve adhesions were not supposed.

A revision with hip replacement arthroplasty was planned.ik

 

 

 

 

 

 

 

 

 

Planning and templating

Preoperatively, magnification-calibrated radiographic study of the femur and pelvis was accomplished. The approximate size of the acetabular cup and femoral stem were determined using acetate template overlaid on radiographs, but with doubts considering the real bone quality of both- the acetabular and femoral components.
Actually, the CT images played a crucial role in the detailed evaluation of the abnormal morphology, present 3 years post FHNO surgery.
Appreciating the femoral component, challenging technical problem was found. A severe proximal femoral canal sclerosis (much more obvious on CT images compared to the pre op X-rays)- Fig.5. This secondary changes always interfere with the well aligned, centralised process of reaming and broaching into the femoral canal. The eccentrically dense bone structure inevitably pushes the canal instruments out of the ideal position, increasing the risk for stem malposition and iatrogenic femoral fracture. This plus the advanced age was appreciated as risk factors for femoral shaft fracture, so a decision for the safer cemented femoral stem (CFX № 7) insertion was made. Because CFX stem have collar, laying against the proximal canal opening, plan was made to correct of the previous FHNO cut, lowering it.pm

Another technical issues were met, evaluating the pelvic component. A flattened, critically shallow acetabulum was found on the CT images, not clearly visible on the radiographs (hidden by the false hoarse bone proliferation). This made the precise cup sizing challenging. The CT (including 3D reconstruction) images, were used for analysis the real bone stock present in the “pseudo acetabulum” area.
The smallest possible cup (24 mmBFX) was templated but still without adequate dorsal bone engagement.

Fortunately, the Biomedtrix THR system offers an unique clinical solution in these difficult cases. Because of the cylindrically shaped press- fit anchoring mechanism , the Biomedtrix BFX cup may offer great stability properties if just adequate cranial and caudal bone contact is achieved. A rarely applied technique of medial acetabulum wall penetration, allows deeper cup insertion , increasing the stability of the implant-Fig.6. vg

This stability is provided by the press-fit cranial and caudal cup edges flush. Logically, the technique demands ideal starting point of the acetabular reaming, because any offset may cause inadvertent dorsal bone loss or devastating acetabular fracture-Fig.7. No option for switching towards cemented cup would be present in these circumstances. So a plan for hybrid THR (BFX cup and CFX stem) was made. Excellent clinical results with hybrid Biomedtrix system were reported (Gemmill TJ, Vet surg, 2011).Untitled-7

 

Surgical protocol

Surgical approach
A standard cranio- lateral approach to the hip joint, including full tenotomy of the deep gluteal muscle, was used. The sciatic nerve was not exposed during the procedure. Advancing through the excessive fibrotic tissue formed at the previous surgical field was extremely challenging and time consuming. It included sharp and blunt tissue dissection. A serious haemorrhage was met from unrecognised arterial vessel in the caudo- distal part of the surgical area. Direct clamping was attempted but not possible, so gauze compression was applied, during the whole procedure.
The replacement arthroplasty was accomplished, following the algorithms and rules provided by the implants manufacturer (more detailed information could be found at http://biomedtrix.com). Only the important technical problems and solutions are described in the following surgery protocol.
A pelvic positioning device was placed underneath the patient, before the aseptic preparation.

Neck resection
A full external femoral rotation to 90 degrees was not possible in the case. The presence of diffuse inelastic fibrotic adhesions, restricted significantly the manipulation of the femur. Two assistants were used to improve the manipulation and retraction at the surgical site. Using a resection guide, aligned with the central axis of the femur, the remnant of the neck was resected according to the preplanned.
A blunt-tipped Hohmann retractor was used to elevate the proximal femur from the wound. Adequate but still more or less suboptimal passage to the canal was achieved.
Femoral canal preparation
Initial opening
The entry point was difficult to visualise because of the solid sclerotic bone, present in the trochanteric fossa. The femoral canal was entered with great care to the alignment, gradually starting with initial 3 mm pin and proceeding with 5 mm drill bit.
Canal preparation
The canal was opened and expanded through reaming of caudal and lateral femoral neck’s walls. Extremely hard cortical bone was found in the caudal and medial femoral neck area. It caused considerable resistance to consequent broaching process. It was physically demanding to resist the tendency of the broach to slide back into malalignment during reinsertion. Small crack fracture (about 3 mm bone fragment) was inevitably caused at the medial wall edge.

No margin of cancellous bone was preserved between the implant and the cortex in the case. Temporary gauze compression of the canal was used to restrict the bleeding, during the following procedure of acteabulum bed preparation. After the BFX cup insertion, the stem was fixed to the femoral canal, using gentamycin impregnated cement.(Biomedtrix 3 G veterinary bone cement) applied by improved pressurised technique (using cement restrictor). No stem centraliser was used in the case.

Acetabular preparation
Meyerding retractors were used to reflected fibrotic soft tissues away of the acetabulum. A Hohmann retractor tip was positioned ventro-caudally of the acetabulum, so a femoral shaft retraction was achieved through a lever arm effect. The visibility to the pelvis was quite satisfactory. An emphasis was put on NOT- starting the acetabular reaming in the dorsally migrated pseudo- acetabulum (nevertheless reliable landmarks were difficult to found). First, the reaming was started approximately 20 degrees to perpendicular, and afterwards changed to the desired cup insertion position. Sequentially larger reamers were used. Very careful and gradual medial wall penetration was accomplished, incrementally testing the acteabular depth with a trial cup. The size of the opening was reasonably big and the periosteum could not be preserved. The toggle pin from a previous surgery was retrieved during the procedure.

Аfter the BFX cup hammering, there was a feeling for solid, and good flushed cup component- Fig.8.index44

 

Post op radiographs evaluation

Excellent implants’ stability and reasonably good orientation were appreciated on the post op X- rays (Fig.9).index55
BFX cup- a mild negative inclination and moderate retroversion was noticed. There was an excellent incorporation within the acetabular bone.
CFX stem- excellently centered in the frontal plane , but caudally tipped in the saggital plane. There was good cement filling, except small cavity in near the medial femoral wall.
Comments
The caudo- distal stem deviation, was probably caused by restricted proximal femur manipulation and suboptimal canal passage availability. It had precluded good alignment broaching and stem insertion- Fig. 10. A potential negative effect of eccentrically placed stems (tip contacting the cortex) could be a creation of stress riser effect and increased risk of femoral fracture, especially if BFX stem is being inserted. The use of cement mold centraliser may had improved the stem orientation, but was unavailable in this case- Fig.11.index8

The small air defect in the cement was probably caused by leakage through the medial wall fragmentation caused intraoperatively.index9

 

Post operative care and follow up

 

Postoperative analgesia included NSAIDs for 4 weeks. The dog was discharged the next day after surgery, with owner instructions for strict cage rest: controlled leash walking only for 10 minutes, 2-3 times daily.
The patient was toe- touching for 5 days post op with gradual increase of the limb usage; real weight bearing 7 days after the surgery. Physiotherapy was restricted to passive range of motion (home exercise).
A close follow-up was performed by phone contact with the owner. Radiographs were repeated at 12 weeks post op- Fig. 12. They revealed good implants stability; a femoral cortex hypertrophy was noticed around the stem tip area. This was appreciated as physiological remodelling due to altered bone stress bearing.index10

 

Results

The patient revealed gradual , but consistent and sustained full clinical improvement. Unrestricted activity was allowed for 12 weeks, when normal (pain free) limb function was appreciated (Video 3). Increased left hind leg muscle mass was found even in this short post op period. Return to normal ROM was found at the recheck (Video 4). Very good perceived quality was reported by the owners.

 

 

CONCLUSIONS

 

Transforming of FHNO to THR is a challenging but viable treatment option, even in severely complicated cases. The Biomedtrix system offers great implants’ design advantages, including combination of hybrid elements; excellent BFX cup anchorage, even in deformed shallow acetabulums.

Difficulties and complications could be faced during the FHNO revisions. These met in this case were manageable, but a higher complication ratio could be expected in similar scenarios. The major causes are the profound morphological changes present after femoral head and neck excision, and the fibrotic adhesions restricting the optimal femoral manipulation during the procedure.

The veterinary professionals , should use FHNO technique wisely, taking into consideration its financial/clinical advantage and disadvantages. The excision arthroplasty should never be suggested as a temporary clinical relief in large breed dogs because more or less it disrupts the normal bio- mechanics, causes length discrepancy and have unpredictable pain relief, requiring prolonged rehabilitation or a revision surgery.
During initial discussions about treatment options, the owners should always be treated fare with evidence based approach and realistically expected results explained. This could protect many dogs from suboptimal functional results, following FHNO recommendation in inappropriate candidates.

REFERENCES
1. Jeffrey N. Peck, Denis J. Marcellin-Little; Advances in small animal total joint replacement ISBN 978-0-470-95961-9
2. Olmstead ML,Hohn RB,TurnerTM:A five-year study of 221 total hip replacements in the dog. J Am Vet Med Assoc 1983;183:191–194
3. Iwata D, Broun HC, Black AP, et al: Total hip arthroplasty outcomes assessment using functional and radio- graphic scores to compare canine systems. Vet Comp Orthop Traumatol 21:221, 2008.

4. BrezonJL,HowardPE,CovellSJ,etal: A retrospective study of the efficacy of femoral head and neck excisions in 94 dogs and cats. Vet Surg 1980;9:88–92
5. Dueland R, Bartel DL, Antonson E: Force-plate technique for canine gait analysis of total hip and excision arthroplasty. J Am Anim Hosp Assoc 13:547, 1977.
6. MontgomeryRD,MiltonJL,HorneRD,etal:A retrospective comparison of three techniques for femoral head and neck excision in dogs. Vet Surg 1987;16:423–426

7. GendreauC,CawleyAJ:Excision of the femoral head and neck: the long term results of 35 operations. J Am Anim Hosp Assoc 1977;13:605–608
8. Excision arthroplasty of the hip joint in dogs and cats. Clinical, radiographic, and gait analysis findings from the Department of Surgery, Veterinary Faculty of the Ludwig-Maximilians-University of Munich, Germany. 1997.
9. DuffR,CampbellJR: Effects of experimental excision arthroplasty of the hip joint. Res Vet Surg 1978;24: 174–181
10. Ganz R: A new periarticular osteotomy for the treatment of hip dysplasia: technique and preliminary results. Clin Orthop 232:26, 1988.
11. Penwick RC: The variables that influence the success of femoral head and neck excision in dogs. Vet Med 87:325, 1992.
12. Mann FA, Tangner CH, Wagner-Mann C, et al: A comparison of standard femoral head and neck excision and femoral head and neck excision using a biceps femoris muscle flap in the dog. Vet Surg 1987;16:223–230
13. Lippincott CL: Improvement of excision arthroplasty of the femoral head and neck utilizing a biceps femoris muscle sling. J Am Anim Hosp Assoc 17:688, 1981.
14. Tarvin G, Lippincott CL: Excision arthroplasty for treat- ment of canine hip dysplasia using the biceps femoris muscle sling: an evaluation of 92 cases. Semin Vet Med Surg Small Anim 2:158, 1987.
15. Duff R, Campbell JR: Effects of experimental excision arthroplasty of the hip joint. Res Vet Sci 23:174, 1978.
16. Duff R, Campbell JR: Radiographic appearance and clinical progress after excision arthroplasty. J Small Anim Pract 19:439, 1978.
17. Lewis DD, Bellah JR, McGavin MD, et al: Postoperative examination of the biceps femoris muscle sling used in excision of the femoral head and neck in dogs. Vet Surg 17:269, 1988.
18. Noel Fitzpatrick, Duniv, MVB, CertSAO, CertVR, Laura Pratola, BSc: Total Hip Replacement after Failed Femoral Head and Neck Excision in Two Dogs and Two Cats .Vet Surg 41 (2012) 136–14
19. GoftonN,Sumner-SmithG:Total hip prosthesis for revision of unsuccessful excision arthroplasty. Vet Surg 1982;11:134–139
20. LiskaWD,DoyleND,SchwartzZ: Successful revision of a femoral head ostectomy (complicated by postoperative sciatic neurapraxia) to a total hip replacement in a cat. Vet Comp Orthop Traumatol 2010;2:119–123