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CASE REPORT
Reverse TPLO for asymmetrical premature closure of the proximal tibial physis in a dog R. M. Demianiuk* and L. P. Guiot*,† *Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA †Department of Veterinary Clinical Sciences, The Ohio State University Veterinary Medical Center at Dublin, 5020 Bradenton Avenue, Dublin, OH 43017, USA
A 4·5-month-old, 13·8 kg, female neutered mixed breed dog was presented for evaluation of acute non-weight bearing right pelvic limb lameness. Radiographs revealed a tibial tuberosity avulsion fracture for which open reduction/internal fixation was performed. Asymmetrical premature closure of the cranial aspect of the proximal tibial physis ensued with a tibial plateau angle of −12°. Abnormal stifle biomechanics resulted in lameness and caudal cruciate ligament fraying. Tibial plateau levelling osteotomy was performed in standard fashion with the exception that the proximal tibial fragment was rotated cranioproximally to increase the tibial plateau angle from −12° to +5° (reverse tibial plateau levelling osteotomy). Normal healing and resolution of lameness followed and the dog remained clinically healthy 2 years postoperatively. This case report demonstrates that any change in proximal tibial anatomy, whether traumatic, iatrogenic or with therapeutic intent, can cause altered stifle biomechanics and should not be underestimated. Surgical management through corrective osteotomy can be used to restore adequate function.
Journal of Small Animal Practice (2014) 55, 589–592 DOI: 10.1111/jsap.12245 Accepted: 6 May 2014; Published online: 24 June 2014
INTRODUCTION Traumatic injuries to the proximal tibial physes are common in dogs and classically repaired using Kirschner wires with or without a tension band wire. Although good outcomes are anticipated, complications including implant migration and premature physeal closure can occur (Goldsmid & Johnson 1991). Premature physeal closure can be either symmetrical or asymmetrical; whereas symmetrical arrest can lead to reduction in overall bone length, an asymmetrical closure is more likely to result in angular deformation proportionate to the amount of residual growth at the time of insult and can significantly alter joint biomechanics and resultant limb function (Rang 2005). While some procedures involving the proximal tibia are designed to alter normal stifle biomechanics (Slocum & Slocum 1993, Warzee et al. 2001, Vezzoni et al. 2008, Montavon et al. 2002, Apelt et al. 2007, Hoffmann et al. 2006), uncontrolled alterations in joint morphology can result in various degrees of functional impairment. This case report documents severe Journal of Small Animal Practice
•
Vol 55
•
November 2014
•
asymmetrical growth of the proximal tibia in the sagittal plane following a tibial tuberosity avulsion fracture and demonstrates the unpredictability associated with premature physeal closure. While this complication associated with tibial tuberosity avulsion fractures has been previously reported (Goldsmid & Johnson 1991), the purpose of this case report is to propose a surgical option for cases in which excessive reduction in the tibial plateau angle (TPA) leads to persistent lameness.
CASE HISTORY A 4·5-month-old (13·8 kg), neutered female mixed breed dog was presented for evaluation of a non-weight bearing right pelvic limb lameness of 3-day duration. Examination identified moderate swelling and pain over the cranial aspect of the right stifle. The remainder of examination was unremarkable and no other pertinent medical history was reported. Radiography of the stifle revealed an avulsion fracture of the tibial tuberosity with mild
© 2014 British Small Animal Veterinary Association
589
R. M. Demianiuk & L. P. Guiot
proximal displacement. There was no involvement of the proximal tibial physis. Open reduction and internal fixation was recommended and subsequently performed under general anaesthesia. Fracture repair was completed using two Kirschner wires (1·6 mm); however, initial postoperative radiographs revealed inappropriate implant positioning with the wires engaging the proximal tibial physis and passing through the epiphysis into the caudomedial aspect of the femorotibial joint space (Fig 1A, B). The implants were appropriately reoriented and supplemented with a tension band wire (0·812 mm) (Fig 1C, D). Postoperative management consisted of a modified Robert-Jones bandage for 24 hours, medical therapy with 2·2 mg/kg carprofen (Pfizer Animal Health) orally twice a day and 2 mg/kg tramadol (McKesson Contract Packaging) orally three times a day to twice a day for 7 days and restricted activity for 6 weeks. Follow-up examination and radiography were recommended to be performed 6 weeks postoperatively. The dog was first returned for follow-up 10 weeks postoperatively when seven months of age. The owners reported a persistent weight bearing lameness with intermittent periods of -weight bearing. Examination revealed moderate muscle atrophy of the right pelvic limb, mild swelling over the tibial tuberosity and pain upon stifle extension. Neither stifle instability nor pain
FIG 1. Initial (A, B) and final (C, D) postoperative radiographs following open reduction and internal fixation of the tibial tuberosity avulsion fracture. (A, B) Originally, the Kirschner wires were inadequately placed as both were engaging the proximal tibial epiphysis and one was protruding into the femoro-tibial joint space. (C, D) Repositioning of the wires with the addition of a tension band wire completed the repair
590
upon palpation of the tibial tuberosity was noted. Radiographs revealed asymmetrical premature closure of the cranial aspect of the proximal tibial physis resulting in a TPA of −12° (Fig 2D–F). Additionally, the tension band wire had slipped off the pins likely because they had not been bent, but no additional changes in implant positioning were noticed. Abnormal stifle biomechanics caused by the cranially tipped plateau slope were suspected to be the cause for persistent lameness. Given the dog’s age and risk of progressive deviation with continued growth, an additional 6 weeks of conservative management was recommended; however, non-weight bearing lameness developed soon thereafter and at eight months of age (12 weeks following the original surgery) revision surgery was planned. Under general anaesthesia, right stifle arthroscopy was initially performed. Findings included mild synovial proliferation with fraying and neovascularization of the caudal cruciate ligament (Fig 3A, B); no additional joint pathology was appreciated (Fig 3C, D). In light of these findings and based on the radiographic findings, tibial plateau levelling osteotomy (TPLO) was selected in an attempt to reduce the forces acting on the caudal cruciate ligament. The previously placed implants were removed and a medial approach to the proximal tibia was made. A standard TPLO was performed with the exception that the proximal tibial fragment was rotated cranioproximally to increase the TPA from −12° to +5°. The required amount of rotation was determined using a traditional TPLO rotation reference chart. Knowing 17° of total TPA correction was required (−12° to +5°), the millimetres of rotation was determined to be the same as a traditional TPLO with a preoperative TPA of +22°, where correction from +22° to +5° also equals 17°. An 18-mm TPLO saw blade (New Generation Devices) was used and 5·5 mm of rotation was completed. The procedure was subsequently termed a reverse TPLO. The osteotomy was stabilised with a standard 3·5mm locking TPLO bone plate (Synthes Inc.) and a pin (2·0 mm) and tension band wire (0·812 mm) to prevent avulsion of the misshapen tuberosity (Fig 4). Postoperative care and recommendations were identical to those after the initial surgery.
FIG 2. Comparative radiographs of the unaffected (A–C) and fractured (D–F) tibiae 10 weeks following open reduction and internal fixation. (A–C) The unaffected tibia showed normal anatomy of its proximal and distal physes and a (B) TPA of ~26°. (D–F) The contralateral side showed (D) complete healing of the fractured tuberosity, (D–F) migration of the tension band wire and (E) severe reduction in the TPA resulting in a tibial plateau angle of −12°
Journal of Small Animal Practice
•
Vol 55
•
November 2014
•
© 2014 British Small Animal Veterinary Association
Reverse TPLO for asymmetrical physeal closure
FIG 3. (A–D) Intraoperative arthroscopic pictures of the right stifle obtained at the time of revision surgery (12 weeks following original trauma). (A) The cranial cruciate ligament and (C, D) menisci [medial (C) and lateral (D)] were normal. (B) Mild synovial proliferation with fraying and neo-vascularization of the caudal cruciate ligament is seen at its femoral origin
FIG 5. (A, B, D) Follow-up postoperative radiographs of the reverse TPLO and (C) a comparative radiograph of the normal contralateral stifle 8 weeks following reverse TPLO (21 weeks following original trauma). Complete healing of the osteotomy site is observed. (A, B) Mild patellar desmitis with evidence of ectopic mineralization is evident on the mediolateral projection. (D) The caudalmost screw of the proximal segment loosened, likely because of a loss in strength due to crossthreading. The rest of the implants remain unchanged with no evidence of complications. The (B) final TPA of the treated stifle is ~6°, whereas (C) the unaffected stifle had a TPA of ~27°
Lastly, recommendations for professional rehabilitation therapy and a gradual return to normal activity were given and pursued by the owner. Final recheck was performed 10 months following reverse TPLO. Functional outcome was reportedly excellent with rare occurrences of temporary discomfort after strenuous activity. At that time, the dog was skeletally mature (23·5 kg) and presented with no evidence of lameness. Muscular mass, range of motion and palpation were identical in both pelvic limbs, with the exception of minimal tenderness upon palpation over the bone plate. Recheck radiographs revealed improving patellar desmitis and remodelling of the osteotomy site. Implant removal was briefly discussed if lameness redeveloped or implant sensitivity persisted. Implant removal has not been required at the time of writing 2 years postoperatively.
DISCUSSION
FIG 4. Immediate postoperative radiographs following reverse TPLO for correction of the negative TPA
Throughout recovery the dog’s lameness progressively improved without evidence of complications. Examination 8 weeks postoperatively revealed mild weight bearing lameness with no pain or crepitus on stifle palpation and normal range of motion. Radiographs revealed complete healing of the osteotomy, mild patellar desmitis and back-out of one of the proximal locking screws (Fig 5). Back-out had been anticipated as it was purposefully angled ~10° proximally to accommodate limited bone stock distally. Journal of Small Animal Practice
•
Vol 55
•
November 2014
•
This report demonstrates that accidental disruption of the cranial aspect of the tibial physis can interfere significantly with proximal tibial growth. As the reason for the premature closure remains speculative, the potential role of iatrogenic trauma cannot be ignored. This emphasises the need for gentle manipulation of tibial tuberosity avulsion fragments and the careful positioning of implants. Furthermore, the use of open approaches is associated with greater iatrogenic tissue trauma, which can be minimised through the use of minimally invasive techniques (Kim et al. 2012) and intraoperative fluoroscopy (Guiot & Déjardin 2012). In the case described here, trauma to the proximal tibial physis resulted in asymmetrical closure of the physis in the sagittal
© 2014 British Small Animal Veterinary Association
591
R. M. Demianiuk & L. P. Guiot
plane. This proximal tibial physeal closure is likely secondary to inadvertent Kirschner wire penetration through this physis during the initial repair of the tibial tuberosity avulsion. However, it cannot be ruled out that the original trauma may have played a role in the development of this complication. Cessation in growth from the cranial aspect alone with continued growth from the caudal aspect resulted in a cranially sloped tibial plateau. Arthroscopic exploration of the stifle revealed mild synovial proliferation in combination with fraying and neovascularization of the caudal cruciate ligament compared to the cranial cruciate ligament, consistent with mechanical overload. These findings correlate with in vitro mechanical studies that showed a TPA of 6·5° neutralises tibial subluxation in the sagittal plane, whereas lower and higher angles induce caudal and cranial tibial thrust, respectively (Warzee et al. 2001). The caudal cruciate ligament has been shown to undergo degeneration in dogs with experimentally induced cranial cruciate ligament transection (Zachos et al. 2002); thus tibial plateau levelling beyond that needed to neutralise cranial tibial thrust may result in further damage to the caudal cruciate ligament. Correcting the negative TPA using a reverse TPLO appeared to be the most appropriate surgical technique to restore more normal stifle biomechanics in this dog. Augmenting the TPA to ~6° was selected based upon the biomechanical considerations established for a cranial cruciate ligament deficient stifle and to prophylactically address this concern in an at risk large breed dog. Additionally, correcting the TPA to a more normal angle (i.e. contralateral stifle TPA ~27°) would have led to significant technical challenges because of the dog’s abnormal tibial conformation. Although back-out of one of the proximal locking screws was not ultimately detrimental to bone healing, in hindsight the authors would have used a standard cortical bone screw within this stacked combi-hole. As previously stated, back-out had been anticipated as this screw was purposefully angled ~10° proximally to accommodate limited bone stock distally. The limited bone stock in this region was the result of proximal fragment rotation in an opposite direction to that of a typically performed TPLO and resultant mismatch of the TPLO bone plate and proximal fragment. Cross-threading of the locking screw and plate hole ensued which resulted in decreased push-out strength and resistance to cantilever bending (Kääb et al. 2004) and the anticipated back-out. Despite cross-threading and preserved screw stability initially, use of a locking screw in this manner violated the principles of this locking system and use of a standard cortical bone screw may have been more appropriate. Iatrogenic asymmetric premature closure of the proximal tibial physis through proximal tibial epiphysiodesis has been suggested as a prophylactic measure in juvenile dogs susceptible to cranial cruciate ligament disease. The technique relies on the hypothesis that residual physeal growth can be halted to induce controlled changes in TPA. The ability to control changes, however, is
592
dependent on the ability to determine residual growth. However, normal mammalian growth is a series of long pauses and sudden bursts (saltation and stasis) which limits the predictability of epiphysiodesis. While an optimal age of four to five months has been suggested (McBrien et al. 2011), this case exemplifies that accidental epiphysiodesis at 4·5 months of age can result in excessive cranial tipping of the tibial plateau with a TPA of −12°. Therefore in summary, premature asymmetrical closure of the proximal tibial physis can lead to significant changes in TPA that may be responsible for secondary damage to the caudal cruciate ligament. This case report demonstrates that any change in proximal tibial anatomy, whether traumatic or with therapeutic intent, can cause altered stifle biomechanics and should not be underestimated. Potential preventive measures to avoid such a complication in a young dog may include weekly rechecks and early implant removal (i.e. 3 to 4 weeks postoperatively). However, if a corrective osteotomy is indicated to restore normal biomechanics then a reverse TPLO may be considered. Conflict of interest None of the authors of this article has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper. References Apelt, D., Kowaleski, M. P. & Boudrieau, R. J. (2007) Effect of tibial tuberosity advancement on cranial tibial subluxation in canine cranial cruciate-deficient stifle joints: an in vitro experimental study. Veterinary Surgery 36, 170-177 Goldsmid, S. & Johnson, K. A. (1991) Complications of canine tibial tuberosity avulsion fractures. Veterinary and Comparative Orthopaedics and Traumatology 4, 54-58 Guiot, L. P. & Déjardin, L. M. (2012) Perioperative imaging in minimally invasive osteosynthesis in small animals. Veterinary Clinics of North America: Small Animal Practice 42, 897-912 Hoffmann, D. E., Miller, J. M., Ober, C. P., et al. (2006) Tibial tuberosity advancement in 65 canine stifles. Veterinary and Comparative Orthopaedics and Traumatology 19, 219-227 Kääb, M. J., Frenk, A., Schmeling, A., et al. (2004) Locked internal fixator: sensitivity of screw/plate stability to the correct insertion angle of the screw. Journal of Orthopaedic Trauma 18, 483-487 Kim, S. E., Hudson, C. C., Pozzi, A. (2012) Percutaneous pinning for fracture repair in dogs and cats. Veterinary Clinics of North America: Small Animal Practice 42, 963-974 McBrien, C. S. J., Vezzoni, A., Conzemius, M. G. (2011) Growth dynamics of the canine proximal tibial physis. Veterinary Surgery 40, 389-394 Montavon, P. M., Damur, D. M., Tepic, S. (2002) Advancement of the tibial tuberosity for the treatment of cranial cruciate deficient stifle. Proceedings of the 1st World Orthopaedic Veterinary Congress. Munich, Germany, September, 2002. p 152 Rang, M. (2005) The physis and skeletal injury. In: Rang’s Children’s Fractures. 3rd edn. Eds D. R. Wenger and M. E. Pring. Lippicott Williams and Wilkins, Philadelphia, PA, USA, pp 11-26 Slocum, B. & Slocum, T. D. (1993) Tibial plateau leveling osteotomy for repair of cranial cruciate ligament rupture in the canine. Veterinary Clinics of North America: Small Animal Practice 23, 777-795 Vezzoni, A., Bohorquez Vanelli, A., Modenato, M., et al. (2008) Proximal tibial epiphysiodesis to reduce tibial plateau slope in young dogs with cranial cruciate ligament deficient stifle. Veterinary and Comparative Orthopaedics and Traumatology 21, 343-348 Warzee, C. C., Déjardin, L. M., Arnoczky, S. P., et al. (2001) Effect of tibial plateau leveling on cranial and caudal tibial thrusts in canine cranial cruciate-deficient stifles: an in vitro experimental study. Veterinary Surgery 30, 278-286 Zachos, T. A., Arnoczky, S. P., Lavagnino, M., et al. (2002) The effect of cranial cruciate ligament insufficiency on caudal cruciate ligament morphology: an experimental study in dogs. Veterinary Surgery 31, 596-603
Journal of Small Animal Practice
•
Vol 55
•
November 2014
•
© 2014 British Small Animal Veterinary Association
CASE REPORT
Reverse TPLO for asymmetrical premature closure of the proximal tibial physis in a dog R. M. Demianiuk* and L. P. Guiot*,† *Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA †Department of Veterinary Clinical Sciences, The Ohio State University Veterinary Medical Center at Dublin, 5020 Bradenton Avenue, Dublin, OH 43017, USA
A 4·5-month-old, 13·8 kg, female neutered mixed breed dog was presented for evaluation of acute non-weight bearing right pelvic limb lameness. Radiographs revealed a tibial tuberosity avulsion fracture for which open reduction/internal fixation was performed. Asymmetrical premature closure of the cranial aspect of the proximal tibial physis ensued with a tibial plateau angle of −12°. Abnormal stifle biomechanics resulted in lameness and caudal cruciate ligament fraying. Tibial plateau levelling osteotomy was performed in standard fashion with the exception that the proximal tibial fragment was rotated cranioproximally to increase the tibial plateau angle from −12° to +5° (reverse tibial plateau levelling osteotomy). Normal healing and resolution of lameness followed and the dog remained clinically healthy 2 years postoperatively. This case report demonstrates that any change in proximal tibial anatomy, whether traumatic, iatrogenic or with therapeutic intent, can cause altered stifle biomechanics and should not be underestimated. Surgical management through corrective osteotomy can be used to restore adequate function.
Journal of Small Animal Practice (2014) 55, 589–592 DOI: 10.1111/jsap.12245 Accepted: 6 May 2014; Published online: 24 June 2014
INTRODUCTION Traumatic injuries to the proximal tibial physes are common in dogs and classically repaired using Kirschner wires with or without a tension band wire. Although good outcomes are anticipated, complications including implant migration and premature physeal closure can occur (Goldsmid & Johnson 1991). Premature physeal closure can be either symmetrical or asymmetrical; whereas symmetrical arrest can lead to reduction in overall bone length, an asymmetrical closure is more likely to result in angular deformation proportionate to the amount of residual growth at the time of insult and can significantly alter joint biomechanics and resultant limb function (Rang 2005). While some procedures involving the proximal tibia are designed to alter normal stifle biomechanics (Slocum & Slocum 1993, Warzee et al. 2001, Vezzoni et al. 2008, Montavon et al. 2002, Apelt et al. 2007, Hoffmann et al. 2006), uncontrolled alterations in joint morphology can result in various degrees of functional impairment. This case report documents severe Journal of Small Animal Practice
•
Vol 55
•
November 2014
•
asymmetrical growth of the proximal tibia in the sagittal plane following a tibial tuberosity avulsion fracture and demonstrates the unpredictability associated with premature physeal closure. While this complication associated with tibial tuberosity avulsion fractures has been previously reported (Goldsmid & Johnson 1991), the purpose of this case report is to propose a surgical option for cases in which excessive reduction in the tibial plateau angle (TPA) leads to persistent lameness.
CASE HISTORY A 4·5-month-old (13·8 kg), neutered female mixed breed dog was presented for evaluation of a non-weight bearing right pelvic limb lameness of 3-day duration. Examination identified moderate swelling and pain over the cranial aspect of the right stifle. The remainder of examination was unremarkable and no other pertinent medical history was reported. Radiography of the stifle revealed an avulsion fracture of the tibial tuberosity with mild
© 2014 British Small Animal Veterinary Association
589
R. M. Demianiuk & L. P. Guiot
proximal displacement. There was no involvement of the proximal tibial physis. Open reduction and internal fixation was recommended and subsequently performed under general anaesthesia. Fracture repair was completed using two Kirschner wires (1·6 mm); however, initial postoperative radiographs revealed inappropriate implant positioning with the wires engaging the proximal tibial physis and passing through the epiphysis into the caudomedial aspect of the femorotibial joint space (Fig 1A, B). The implants were appropriately reoriented and supplemented with a tension band wire (0·812 mm) (Fig 1C, D). Postoperative management consisted of a modified Robert-Jones bandage for 24 hours, medical therapy with 2·2 mg/kg carprofen (Pfizer Animal Health) orally twice a day and 2 mg/kg tramadol (McKesson Contract Packaging) orally three times a day to twice a day for 7 days and restricted activity for 6 weeks. Follow-up examination and radiography were recommended to be performed 6 weeks postoperatively. The dog was first returned for follow-up 10 weeks postoperatively when seven months of age. The owners reported a persistent weight bearing lameness with intermittent periods of -weight bearing. Examination revealed moderate muscle atrophy of the right pelvic limb, mild swelling over the tibial tuberosity and pain upon stifle extension. Neither stifle instability nor pain
FIG 1. Initial (A, B) and final (C, D) postoperative radiographs following open reduction and internal fixation of the tibial tuberosity avulsion fracture. (A, B) Originally, the Kirschner wires were inadequately placed as both were engaging the proximal tibial epiphysis and one was protruding into the femoro-tibial joint space. (C, D) Repositioning of the wires with the addition of a tension band wire completed the repair
590
upon palpation of the tibial tuberosity was noted. Radiographs revealed asymmetrical premature closure of the cranial aspect of the proximal tibial physis resulting in a TPA of −12° (Fig 2D–F). Additionally, the tension band wire had slipped off the pins likely because they had not been bent, but no additional changes in implant positioning were noticed. Abnormal stifle biomechanics caused by the cranially tipped plateau slope were suspected to be the cause for persistent lameness. Given the dog’s age and risk of progressive deviation with continued growth, an additional 6 weeks of conservative management was recommended; however, non-weight bearing lameness developed soon thereafter and at eight months of age (12 weeks following the original surgery) revision surgery was planned. Under general anaesthesia, right stifle arthroscopy was initially performed. Findings included mild synovial proliferation with fraying and neovascularization of the caudal cruciate ligament (Fig 3A, B); no additional joint pathology was appreciated (Fig 3C, D). In light of these findings and based on the radiographic findings, tibial plateau levelling osteotomy (TPLO) was selected in an attempt to reduce the forces acting on the caudal cruciate ligament. The previously placed implants were removed and a medial approach to the proximal tibia was made. A standard TPLO was performed with the exception that the proximal tibial fragment was rotated cranioproximally to increase the TPA from −12° to +5°. The required amount of rotation was determined using a traditional TPLO rotation reference chart. Knowing 17° of total TPA correction was required (−12° to +5°), the millimetres of rotation was determined to be the same as a traditional TPLO with a preoperative TPA of +22°, where correction from +22° to +5° also equals 17°. An 18-mm TPLO saw blade (New Generation Devices) was used and 5·5 mm of rotation was completed. The procedure was subsequently termed a reverse TPLO. The osteotomy was stabilised with a standard 3·5mm locking TPLO bone plate (Synthes Inc.) and a pin (2·0 mm) and tension band wire (0·812 mm) to prevent avulsion of the misshapen tuberosity (Fig 4). Postoperative care and recommendations were identical to those after the initial surgery.
FIG 2. Comparative radiographs of the unaffected (A–C) and fractured (D–F) tibiae 10 weeks following open reduction and internal fixation. (A–C) The unaffected tibia showed normal anatomy of its proximal and distal physes and a (B) TPA of ~26°. (D–F) The contralateral side showed (D) complete healing of the fractured tuberosity, (D–F) migration of the tension band wire and (E) severe reduction in the TPA resulting in a tibial plateau angle of −12°
Journal of Small Animal Practice
•
Vol 55
•
November 2014
•
© 2014 British Small Animal Veterinary Association
Reverse TPLO for asymmetrical physeal closure
FIG 3. (A–D) Intraoperative arthroscopic pictures of the right stifle obtained at the time of revision surgery (12 weeks following original trauma). (A) The cranial cruciate ligament and (C, D) menisci [medial (C) and lateral (D)] were normal. (B) Mild synovial proliferation with fraying and neo-vascularization of the caudal cruciate ligament is seen at its femoral origin
FIG 5. (A, B, D) Follow-up postoperative radiographs of the reverse TPLO and (C) a comparative radiograph of the normal contralateral stifle 8 weeks following reverse TPLO (21 weeks following original trauma). Complete healing of the osteotomy site is observed. (A, B) Mild patellar desmitis with evidence of ectopic mineralization is evident on the mediolateral projection. (D) The caudalmost screw of the proximal segment loosened, likely because of a loss in strength due to crossthreading. The rest of the implants remain unchanged with no evidence of complications. The (B) final TPA of the treated stifle is ~6°, whereas (C) the unaffected stifle had a TPA of ~27°
Lastly, recommendations for professional rehabilitation therapy and a gradual return to normal activity were given and pursued by the owner. Final recheck was performed 10 months following reverse TPLO. Functional outcome was reportedly excellent with rare occurrences of temporary discomfort after strenuous activity. At that time, the dog was skeletally mature (23·5 kg) and presented with no evidence of lameness. Muscular mass, range of motion and palpation were identical in both pelvic limbs, with the exception of minimal tenderness upon palpation over the bone plate. Recheck radiographs revealed improving patellar desmitis and remodelling of the osteotomy site. Implant removal was briefly discussed if lameness redeveloped or implant sensitivity persisted. Implant removal has not been required at the time of writing 2 years postoperatively.
DISCUSSION
FIG 4. Immediate postoperative radiographs following reverse TPLO for correction of the negative TPA
Throughout recovery the dog’s lameness progressively improved without evidence of complications. Examination 8 weeks postoperatively revealed mild weight bearing lameness with no pain or crepitus on stifle palpation and normal range of motion. Radiographs revealed complete healing of the osteotomy, mild patellar desmitis and back-out of one of the proximal locking screws (Fig 5). Back-out had been anticipated as it was purposefully angled ~10° proximally to accommodate limited bone stock distally. Journal of Small Animal Practice
•
Vol 55
•
November 2014
•
This report demonstrates that accidental disruption of the cranial aspect of the tibial physis can interfere significantly with proximal tibial growth. As the reason for the premature closure remains speculative, the potential role of iatrogenic trauma cannot be ignored. This emphasises the need for gentle manipulation of tibial tuberosity avulsion fragments and the careful positioning of implants. Furthermore, the use of open approaches is associated with greater iatrogenic tissue trauma, which can be minimised through the use of minimally invasive techniques (Kim et al. 2012) and intraoperative fluoroscopy (Guiot & Déjardin 2012). In the case described here, trauma to the proximal tibial physis resulted in asymmetrical closure of the physis in the sagittal
© 2014 British Small Animal Veterinary Association
591
R. M. Demianiuk & L. P. Guiot
plane. This proximal tibial physeal closure is likely secondary to inadvertent Kirschner wire penetration through this physis during the initial repair of the tibial tuberosity avulsion. However, it cannot be ruled out that the original trauma may have played a role in the development of this complication. Cessation in growth from the cranial aspect alone with continued growth from the caudal aspect resulted in a cranially sloped tibial plateau. Arthroscopic exploration of the stifle revealed mild synovial proliferation in combination with fraying and neovascularization of the caudal cruciate ligament compared to the cranial cruciate ligament, consistent with mechanical overload. These findings correlate with in vitro mechanical studies that showed a TPA of 6·5° neutralises tibial subluxation in the sagittal plane, whereas lower and higher angles induce caudal and cranial tibial thrust, respectively (Warzee et al. 2001). The caudal cruciate ligament has been shown to undergo degeneration in dogs with experimentally induced cranial cruciate ligament transection (Zachos et al. 2002); thus tibial plateau levelling beyond that needed to neutralise cranial tibial thrust may result in further damage to the caudal cruciate ligament. Correcting the negative TPA using a reverse TPLO appeared to be the most appropriate surgical technique to restore more normal stifle biomechanics in this dog. Augmenting the TPA to ~6° was selected based upon the biomechanical considerations established for a cranial cruciate ligament deficient stifle and to prophylactically address this concern in an at risk large breed dog. Additionally, correcting the TPA to a more normal angle (i.e. contralateral stifle TPA ~27°) would have led to significant technical challenges because of the dog’s abnormal tibial conformation. Although back-out of one of the proximal locking screws was not ultimately detrimental to bone healing, in hindsight the authors would have used a standard cortical bone screw within this stacked combi-hole. As previously stated, back-out had been anticipated as this screw was purposefully angled ~10° proximally to accommodate limited bone stock distally. The limited bone stock in this region was the result of proximal fragment rotation in an opposite direction to that of a typically performed TPLO and resultant mismatch of the TPLO bone plate and proximal fragment. Cross-threading of the locking screw and plate hole ensued which resulted in decreased push-out strength and resistance to cantilever bending (Kääb et al. 2004) and the anticipated back-out. Despite cross-threading and preserved screw stability initially, use of a locking screw in this manner violated the principles of this locking system and use of a standard cortical bone screw may have been more appropriate. Iatrogenic asymmetric premature closure of the proximal tibial physis through proximal tibial epiphysiodesis has been suggested as a prophylactic measure in juvenile dogs susceptible to cranial cruciate ligament disease. The technique relies on the hypothesis that residual physeal growth can be halted to induce controlled changes in TPA. The ability to control changes, however, is
592
dependent on the ability to determine residual growth. However, normal mammalian growth is a series of long pauses and sudden bursts (saltation and stasis) which limits the predictability of epiphysiodesis. While an optimal age of four to five months has been suggested (McBrien et al. 2011), this case exemplifies that accidental epiphysiodesis at 4·5 months of age can result in excessive cranial tipping of the tibial plateau with a TPA of −12°. Therefore in summary, premature asymmetrical closure of the proximal tibial physis can lead to significant changes in TPA that may be responsible for secondary damage to the caudal cruciate ligament. This case report demonstrates that any change in proximal tibial anatomy, whether traumatic or with therapeutic intent, can cause altered stifle biomechanics and should not be underestimated. Potential preventive measures to avoid such a complication in a young dog may include weekly rechecks and early implant removal (i.e. 3 to 4 weeks postoperatively). However, if a corrective osteotomy is indicated to restore normal biomechanics then a reverse TPLO may be considered. Conflict of interest None of the authors of this article has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper. References Apelt, D., Kowaleski, M. P. & Boudrieau, R. J. (2007) Effect of tibial tuberosity advancement on cranial tibial subluxation in canine cranial cruciate-deficient stifle joints: an in vitro experimental study. Veterinary Surgery 36, 170-177 Goldsmid, S. & Johnson, K. A. (1991) Complications of canine tibial tuberosity avulsion fractures. Veterinary and Comparative Orthopaedics and Traumatology 4, 54-58 Guiot, L. P. & Déjardin, L. M. (2012) Perioperative imaging in minimally invasive osteosynthesis in small animals. Veterinary Clinics of North America: Small Animal Practice 42, 897-912 Hoffmann, D. E., Miller, J. M., Ober, C. P., et al. (2006) Tibial tuberosity advancement in 65 canine stifles. Veterinary and Comparative Orthopaedics and Traumatology 19, 219-227 Kääb, M. J., Frenk, A., Schmeling, A., et al. (2004) Locked internal fixator: sensitivity of screw/plate stability to the correct insertion angle of the screw. Journal of Orthopaedic Trauma 18, 483-487 Kim, S. E., Hudson, C. C., Pozzi, A. (2012) Percutaneous pinning for fracture repair in dogs and cats. Veterinary Clinics of North America: Small Animal Practice 42, 963-974 McBrien, C. S. J., Vezzoni, A., Conzemius, M. G. (2011) Growth dynamics of the canine proximal tibial physis. Veterinary Surgery 40, 389-394 Montavon, P. M., Damur, D. M., Tepic, S. (2002) Advancement of the tibial tuberosity for the treatment of cranial cruciate deficient stifle. Proceedings of the 1st World Orthopaedic Veterinary Congress. Munich, Germany, September, 2002. p 152 Rang, M. (2005) The physis and skeletal injury. In: Rang’s Children’s Fractures. 3rd edn. Eds D. R. Wenger and M. E. Pring. Lippicott Williams and Wilkins, Philadelphia, PA, USA, pp 11-26 Slocum, B. & Slocum, T. D. (1993) Tibial plateau leveling osteotomy for repair of cranial cruciate ligament rupture in the canine. Veterinary Clinics of North America: Small Animal Practice 23, 777-795 Vezzoni, A., Bohorquez Vanelli, A., Modenato, M., et al. (2008) Proximal tibial epiphysiodesis to reduce tibial plateau slope in young dogs with cranial cruciate ligament deficient stifle. Veterinary and Comparative Orthopaedics and Traumatology 21, 343-348 Warzee, C. C., Déjardin, L. M., Arnoczky, S. P., et al. (2001) Effect of tibial plateau leveling on cranial and caudal tibial thrusts in canine cranial cruciate-deficient stifles: an in vitro experimental study. Veterinary Surgery 30, 278-286 Zachos, T. A., Arnoczky, S. P., Lavagnino, M., et al. (2002) The effect of cranial cruciate ligament insufficiency on caudal cruciate ligament morphology: an experimental study in dogs. Veterinary Surgery 31, 596-603
Journal of Small Animal Practice
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Vol 55
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November 2014
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© 2014 British Small Animal Veterinary Association
