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


Dr. Vladislav Zlatinov,

Corresponding author :

Dr. Vladislav Zlatinov,

Central Veterinary Clinic

Chavdar Mutafov str, 25 B, Sofia, Bulgaria






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.




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 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 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 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 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 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 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 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 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 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 Segmental epidural analgesia


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











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 Microscope- assisted arterial anastomosis











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.















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.).




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




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 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 Three weeks post op


Fig.22 Six months post op


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.








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


Dr. Vladislav Zlatinov

Corresponding author :

Dr. Vladislav Zlatinov,
Central Veterinary Clinic
Chavdar Mutafov str, 25 B, Sofia, Bulgaria

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




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.



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

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 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.
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



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.





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.

1. Jeffrey N. Peck, Denis J. Marcellin-Little; Advances in small animal total joint replacement ISBN 978-0-470-95961-9
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