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Equine vet. J . ( I 992) 24 (4) 264-268
Clinical and radiographic features, treatment and outcome in 15 horses with fracture of the medial aspect of the patella SUE DYSON, 1. WRIGHT, S. KOLD and N. VATISTAS Equine Clinical Unit, Animal Health Trust, Snailwell Road, Newmarket, Suffolk CB8 7DW, UK Summary
lateromedial view was also obtained in 6 horses.
A sagittal fracture of the medial aspect of the patella was Treatment identified in 15 horses, 2 of which had been kicked and 12 of which had hit a fixed fence while jumping. Eight horses showed One horse (No. 15) was humanely destroyed at the request of the concurrent fragmentation of the base of the patella, and 2 had owner. In Horse 14 the patellar fracture was initially repaired by sustained a concurrent fracture of the distal end of the lateral internal fixation, but the implant failed and the fracture fragment trochlear ridge of the femur. A cranioproximal-craniodistal was subsequently removed. Bone fragments in the distal aspect of oblique radiographic view was essential to identify the site of the the femoropatellar joint were removed from Horses 7 and 13, and a medial patellar fracture and to determine its configuration. non-displaced patellar fracture treated conservatively. However, the Fourteen horses were treated by surgical removal of the medial fracture fragment subsequently displaced and was ultimately patellar fracture fragment@). Of 12 horses (83%) without removed. The remaining horses (1-6, and 8-12) were treated by evidence of preexisting degenerative joint disease, 10 were surgical removal of the medial patellar fracture fragment(s). Fragmentation of the base of the patella was treated conservatively. treated successfully with return to full athletic function.
Introduction
Surgical techniquefor partial patellectomy
THERE are few reports in the literature concerning treatment of patellar fractures in the horse (Aldrete and Meagher 1981; Dik and Nemeth 1983; Colbern and Moore 1984; Pankowski and White 1985; Parks and Wyn-Jones 1988). Norrie (1982). Turner (1984) and Stashak (1987) suggested that articular fractures of the patella in horses carry a poor prognosis. In one series of 5 horses treated conservatively, only 2 recovered (Dik and Nemeth 1983), whereas a few case reports have indicated that prognosis may be improved by partial patellectomy (Colbern and Moore 1984; Pankowski and White 1985; Parks and Wyn-Jones 1988) or internal fixation (DeBowes, Grant, Chalman and Rantanen 1980 Aldrete and Meagher 1981). The purpose of this paper is to describe the history, clinical and radiographic features, treatment by partial patellectomy and outcome of 15 articular, sagittal fractures involving the medial aspect of the patella.
All horses were premedicated with im acepromazine (0.05 m@g bwt). Sedation was achieved with xylazine (I. 1 m a g bwt, iv) or detomidine (0.002 m a g bwt, iv), occasionally with the addition of butorphanol (0.001 m a g bwt, iv). Anaesthesia was induced with thiopentone (5 m a g bwt, iv) or ketamine (2.2 m a g bwt, iv), and maintained with a mixture of halothane in oxygen. Each horse was positioned in dorsal recumbency or in lateral recumbency with the affected limb lowermost. After preparing the site for aseptic surgery, a 15-25 cm curvilinear incision was made over the medial aspect of the femoropatellar joint, centred over the patella or the displaced fragment. The incision was continued through the subcutaneous tissues and the thick fascia associated with the insertions of the sartorius and gracilis muscles, into the femoropatellar joint. When possible the femoropatellar joint capsule was identified before being incised. The fracture fragment or fracture plane was identified by palpation, and the fragment was sharply dissected free from its soft tissue attachments. This involved the severance of a substantial or entire portion of the medial patellar and medial femoropatellar ligaments and part of the tendon of insertion of the vastus medialis. In more chronic cases, the fibrous tissue present between the fragment and parent bone was incised. In some cases the entire medial patellar cartilage was removed with the fracture fragment. A curette and/or rongeurs were used to debride and contour the parent bone. The trochlear ridges of the distal femur were examined for any concurrent damage or signs of degenerative joint disease. The joint was liberally flushed with either sterile saline and sodium penicillin, or a polyionic electrolyte solution (Hartmanns’ solution, Baxter Healthcare, Ltd., Compton, Newbury, Berks., UK). The joint capsule (when possible), the insertion of sartorius and gracilis, and the subcutaneous tissues were individually
Materials and methods An articular fracture of the medial aspect of the patella was diagnosed in 15 horses referred to the Equine Clinical Unit of the Animal Health Trust, between August 1984 and August 1990. The history of each horse was documented and a comprehensive clinical examination performed.
Radiographic examination Radiographic examination of the stifle was performed in the standing horse by using rare earth screens and orthochromatic G film (Kodak). All examinations included caudocranial, caudolateral-craniomedial oblique and cranioproximalcraniodistal oblique views (Butler et al 1992). A flexed
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TABLE 1: Descrlptlon, hlstory, radlographlc features, treatment and outcome of 15 horses with a patellar fracture Age Horse (years) Occupation
History (duration of lameness)
Radiographic features
Treatment
Outcome
Non-displaced comminuted fracture medial 1/4 of patella. Abnormal opacity of patella in LM view Displaced comminuted fracture medial 1/3 of patella. Abnormal opacity of patella in LM view. Degenerativejoint disease
Surgical removal of fracture fragments
Returned to full function: novice horse trials Lame (degenerative joint disease)
1
13
E
Kicked (8 weeks)
2
4
H
Kicked (19 weeks)
3
6
E
Lame in field (10 days)
4
7
E
5
7
E
Hit cross country fence (c24 h) Hit cross country fence (5 weeks)
6
8
E
Hit cross country fence (8 months)
7
8
E
Hit cross country fence (3 weeks)
7
E
10
E
Hit cross country fence (10 days) Hit cross country fence (4 days)
10
7
E
Hit cross country fence (11 days)
11
9
E
12
10
E
13
9
E
14
9
H
15
6
E
Lame associated with new bone formation at cranial aspect of fracture plane Surgical removal of Returned to full function: Slight fragmentation of base of Hit cross country fence patella. Slightly displaced fracture medial patellar fracture advanced horse trials of medial 1/6 of patella (c24 h) Non-displaced fracture medial 1/4 (i) Arthroscopic removal Returned to full function: Hit cross intermediate horse trials country fence of patella. Several small fragments of small fragments in distal aspect of femoropatellar (ii) Surgical removal of (9days) joint medial patellar fracturet (i) Internal fixation: Returned to full function: Displaced fracture medial 1/3 of Hit fence implants failed hunting jumping out of patella (ii) Surgical removal of field (2 weeks) medial patellar fracture Slight fragmentation of base of None Humanely destroyed Hit cross (owner's request) country fence patella. Displaced fracture of medial 1/4 of patella. Comminuted (c24 h) fracture of distal aspect of lateral trochlear ridge of femur Hit cross country fence (2 weeks)
Surgical removal of fracture fragments (confirmed preexisting degenerative joint disease) Surgical removal of medial patellar fracture (Tears noted in joint capsule) Surgical removal of medial patellar fracture Surgical removal of medial patellar fracture
Fragmentation of base of patella and small slightly displaced fracture of medial pole of patella Fragmentation of base of patella. Displaced fracture of medial 114 of patella Slight irregularity of outline of proximal aspect of patella. Displaced fracture of medial 116 of patella Fragmentation of base of patella. Surgical removal of medial patellar Displaced fracture medial 1/4 of patella. Degenerativejoint disease fracture (confirmed preexisting degenerative joint disease) Fragmentationof base of patella. (i) Arthroscopic removal of trochlear ridge Marginally displaced fracture of medial 1/4 of patella. Comminuted f ragments (ii) Surgical removal of fracture distal aspect of lateral medial patellar fracturet trochlear ridge of femur Surgical removal of Slight fragmentation of base of medial patellar fracture patella. Displaced fracture of medial 1/5 of patella Fragmentationof base of patella. Surgical removal of medial patellar fracture Dimlaced fracture of medial 1/4 and loose fragments of patella. Several fragments in distal aspect of femoropatellar joint Surgical removal of Displaced fracture medial 1/4 of patella. Several ill-defined medial patellar fracture opacities in distal aspect of femoropatellar joint Surgical removal of Slight fragmentation of base of patella. Displaced fracture medial medial patellar 1/5 of patella fracture
Returned to full function: novice horse trials Returned to full function: advanced horse trials Returned to full function: novice horse trials Lame (degenerativejoint disease)
Returned to full function: intermediate horse trials
Returnedto full function: intermediate horse trials Humanely destroyed (luxated patella in recovering from general anaesthesia) Returned to full function: intermediate horse trials
'E, eventing; H, hunting. +The initially non-displaced patellar fracture became displaced
closed with either three or five metric polyglactin 910 (Vicryl; Ethicon, Edinburgh, UK) or 3 metric polyglycolic acid (Dexon; Davies and Geck, Gosport, Hampshire, UK) in either a simple interrupted or simple continuous suture pattern. The skin was apposed with three metric monofilament nylon (Ethilon; Ethicon) in a vertical or horizontal mattress or simple interrupted suture
pattern, and a stent bandage was oversewn. Post-operative management
Sodium penicillin (iv, 3 times/day) or procaine penicillin (im, twice/day) (22,000 iuhcg bwt) was administered, starting at 30
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Table 2: Radlographlc features of 15 fractures of the medlal aspect of the patella Caudolateral-craniomedial oblique and lateromedial view No abnormality of patella Fragmentation of base of patella One or more large fragments proximal to patella Irregular opacity of patella Small fragments in distal aspect of femoropatellar joint Comminuted fracture of distal end of lateral trochlear ridge of femur
1
8 6' 2
3' 2
Cranioproximal-craniodistal oblique view Non-displaced simple articular fracture Displaced simple articular fracture Non-displaced comminuted articular fracture Displaced comminuted fracture
2t 11 1 1
'Unable to determine source of fragment(s).t2 non-displaced fractures which were treated conservatively initially, subsequently became displaced
Fig I : Cranioproximal-craniodisfoloblique view of a patella (Horse 12). There is a non-displaced fracture of its medial pole. The fracture fragment was removed, leaving the medial patellar cartilage intact
Fig 2: Cranioproximal-craniodistaloblique view of a patella (Horse 4 ) . There is a displacedfracture ofthe medial aspect ($the patella
Fig 4: Caudolateral-craniomedialoblique view of a stQle (Horse 7). There is a comminuted fracture c$ the distal aspect of the lateral rrochlear ridge. A fracture of the medial aspect of' the patella was not seen. but was confirmed on a CrPr-CrDiO view
History and clinical signs are summarised in Table I . Twelve of
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comminuted fracture of the distal end of the lateral trochlear ridge of the femur (Fig 4).Two horses (Nos 2 and 6) had evidence of degenerative joint disease. Perioperative complications
Horse 4 had considerable periarticular soft tissue swelling, despite treatment with non-steroidal anti-inflammatory drugs, when operated on 6 days after the onset of lameness. It recovered poorly from general anaesthesia, and there was considerable haemorrhage from the wound. The distal one-third of the incision subsequently dehisced, but healed by second intention with a good cosmetic outcome. Horse 9 had a catastrophic recovery from general anaesthesia: the patella luxated laterally and the horse was humanely destroyed. Post-mortem examination revealed evidence of pre-operative haemorrhage in the quadriceps muscles and subsequent avulsion of the patellar fibrocartilage and a fracture of the lateral proximal tibia. Horse 14, treated initially by internal fixation using 2 lag screws, made good progress until Day 20 after operation when severe lameness ensued. This was associated with displacement of the fracture and the distal screw and breakage of the proximal screw. The fracture fragment was subsequently removed successfully. Both horses (Nos 7 and 13) in which a nondisplaced patellar fracture was initially treated conservatively, following arthroscopic removal of small fracture fragments from the distal aspect of the femoropatellar joint, subsequently underwent a second surgical procedure to remove the medial patellar fracture fragment due to its displacement (Fig 5). Follow up
(W Fig 5: Cranioproximal-craniodistaloblique views of the patella of Horse 13: (a) 9 days and (b) 63 days ajier the onset of lameness. The nondisplaced fracture (a)subsequently displaced (b)
the 15 horses had hit a fixed fence, I I whilst in competition (horse trials). Although several of these horses completed the cross-country course, the majority pulled up lame shortly after hitting the fence. Some of the riders could not recall the horse hitting a fence but this was always subsequently verified by fence judges or spectators. Two horses had been kicked. Most horses would bear full weight on the limb but were inclined to stand with the heel elevated and the limb partly flexed. Distension of the femoropatellar joint capsule and a variable amount of localised periarticular soft tissue swelling usually developed within 24 h. Palpable or audible crepitus was a variable feature. Horses usually resented full flexion of the limb, but tolerated well the limb being held in the 'shoeing' position. The initial degree of lameness at the walk and the trot varied from moderate to severe, and persisted, albeit improving slightly over the following days. Radiographic examinations
In all horses a cranioproximal-craniodistaloblique (CrPr-CrDiO) view was essential to identify the site of a fracture of the patella and to confirm its configuration (Table 2) (Figs I and 2). In 8 horses there was slight fragmentation of the base of the patella (Fig 3) seen in a caudolateral-craniomedial oblique (CdL-CrMO) or lateromedial (LM) views (Table 2). One or more fragments of undetermined source were seen proximal to the patella in 6 horses in CdL-CrMO or LM views, and small fragments in the distal aspect of the femoropatellar joint were seen in 3 horses (Nos 9, 10 and 13). Two horses (Nos 7 and 15) had sustained a concurrent
One horse (No. 15) was humanely destroyed at the owner's request (Table I ) and a second horse (No. 9) was destroyed after complications during recovery from anaesthesia. l k o horses with pre-existing degenerative joint disease (Nos 2 and 6) which presented 10 weeks and 8 months respectively after onset of lameness were considerably improved but remained lame. Of the remaining I I horses, 10 have returned to full athletic function at the same or higher level than pre-operatively. None of these horses has experienced recurrent lameness related to the stifle in the period of follow-up (8 months to 7 years). Eight of these horses have been re-examined radiographically 3 months to 3 years post-operatively and none has shown evidence of modelling or fragmentation of the apex of the patella, or other secondary changes. Several horses showed mild hindlimb stiffness when work was first resumed but as work intensity increased and symmetrical hindlimb musculature was redeveloped, these minor gait abnormalities resolved. The cosmetic result was good in all cases.
Discussion The most common cause of patellar fractures is trauma (Hickman 1964; Aldrete and Meagher 1981; Colbern and Moore 1984; Pankowski and White 1985; Parks and Wyn-Jones 1988), usually as a result of a kick or hitting a jump. In the present series 12 of 15 horses hit a fixed obstacle while jumping. In this insfance the impact on the patella occurs when the stifle is partly flexed and the bone is fixed in the femoral trochlea (Pankowski and White 1985). Dik and Nemeth (1983) suggested that extreme muscle contractions may lead to avulsion of the medial patellar angle. However, no such history was recorded in the present series and other authors (Hickman 1964; Pankowski and White 1985) have suggested that intense contraction of the quadriceps group is more likely to cause a fracture orientated along soft tissue attachments or across the body of the patella. The experiencespf this series suggest that early radiographic
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examination is indicated in horses with known trauma to the stifle region after hitting a fixed fence. Even if abnormalities are detected in caudocranial, CdL-CrMO or LM views, a CrPr-CrDiO view should be included, since otherwise a patellar fracture may be missed. Evidence of degenerative joint disease appears to warrant a more guarded prognosis for return to athletic function. The results of this series indicate that apparently stable, nondisplaced fractures may become displaced, and since degenerative joint disease is a likely sequel to an articular fracture, surgical management is the treatment of choice, confirming the conclusions of Norrie ( I 982). Dik and Nemeth ( I 983), Turner (1984). Stashak (1987) and Auer (1991). Pre-operative appraisal should include a careful clinical examination and a close scrutiny of a complete set of radiographs. We failed to detect damage to the quadriceps muscles of Horse 9 pre-operatively. and the patella luxated laterally during recovery from anaesthesia. Based upon this case, and Horse 4 which had extensive periarticular soft tissue swelling pre-operatively and subsequently experienced partial wound dehiscence, we recommend that surgery should be delayed until the acute inflammatory response has subsided. The potential for primary failure of the surgical closure of the medial parapatellar incision must always be borne in mind. Concurrent fragmentation of the base of the patella was treated conservatively. Such fragmentation has been seen alone after hitting a fixed fence when jumping, and associated lameness has resolved following box rest and controlled walking exercise for 8-12 weeks (S. Dyson, unpublished data). The results of follow-up radiography indicate that in some cases the fragments disappear, presumably by healing the parent bone or resorption, whereas in others they persist for a long time unassociated with lameness. Aldrete and Meagher ( I98 I ) reported the successful repair of a simple sagittal fracture of the medial one-third of the patella by internal fixation. In contrast to Horse 14, 3 rather than 2 4.5-mm SIF cortical bone screws were inserted using the lag principle to stabilise the fragment. Aldrete and Meagher (198 I ) and Trotter, McIlwraith and Norrdin (1983) suggest that, after a stifle arthrotomy. horses should be cross-tied to prevent recumbency and the associated excessive wound tension developing due to flexion. Although cross-tying may have benefitted the case in the present material, the failure of the implants did not occur until almost 3 weeks after surgery. The use of 5.5-mm ASIF cortical screws may also have advantages in preventing breakage and dislocation of the implants. Partial patellectomy is a relatively straightforward surgical procedure, removing the problems of accurate fracture reduction, and screw placement, and possible implant failure. The results of this case series strongly support the encouraging case reports of Colbem and Moore (1984), Pankowski and White (1985) and Parks and Wyn-Jones (1988) and provide much longer follow-up data (8 months to 7 years) in a group of predominantly competition horses. In this series 10 of 12 horses (83%) without evidence of pre-existing degenerative joint disease were treated successfully with full return to athletic function, 2 of which have competed internationally. Concurrent fractures of the distal aspect of the lateral trochlear ridge did not appear to affect the outcome adversely. In the immediate post-operative period the horses were allowed to lie down and only one horse (No. 4) had secondary complications which were probably related to premature surgery
and further trauma sustained during recovery from anaesthesia. To minimise the risks of post-operative complications the surgical technique could be modified by examining the fracture arthroscopically, identifying it with needles and then making a small incision directly over the fragment. The surgical procedure involved transection of the medial patellar ligament and in most cases removal of the medial patellar cartilage. However. in this series no complications arose in contrast to the report of McIlwraith (1990) and Gibson, McIlwraith, Park and Norrdin (1989) following clinical or experimental medial patellar desmotomy. This may reflect the small number in the case series (although comparable to the report of Gibson el a/ (1989)). or altered biomechanical forces following removal of part of the patella per se. In conclusion, we strongly recommend treatment of medial patellar fractures by partial patellectomy but caution the reader to evaluate each horse carefully, both clinically and radiographically, to detect concurrent soft tissue or bony pathology which may adversely influence the outcome.
Acknowledgements We thank the referring veterinarians and the staff of the Equine Clinical Unit of the Animal Health Trust; and Jan Butler for preparing the illustrations. N. J. Vatistas is supported by a generous grant from the Marjorie Coote Animal Charity Trust.
References Aldrete. A.V. and Meagher. D.M. (1981) Lag screw fixation of a patellar fracture in a horse. Vef. Surg. 10. 143-148. Auer. J. (1991) In: Equine Medicine and Surgery. 4th edn. Vol 11. Eds: P. Colahan. J. Mayhew. A. Merritt. and 1. Moore. American Veterinary Publications. Santa Barbara. pp 1489-1491. Butler. J.. Colles. C.. Dyson. S.. Kold. S. and Poulos, P. (1992) Clinical Radiology of'fhe Horse. Blackwell Scientific Publications.Oxford. Colbem. G.T. and Moore, J.N. (1984) Surgical management of proximal articular fracture of the patella in a horse. J. Am. w f . med. Ass. 185,543-545. DeBowes. R.. Grant. B.. Chalman. J. and Rantanen. N. (1980) Fractured patella in a horse. Equine Pracfice 2.49-53. Dik, K.J. and Nemeth. F. (1983) Traumatic patellar fractures in the horse. Equine vet. J. 15.244-247. Gibson. K.. Mcllwraith. C., Park, R. and Norrdin, R. (1989) Production of patellar lesions by medial patellar desmotomy in normal horses. Vef. Surg. 18, 466-471. Hickman. J. (1964) V e f e r i w v Onhopuedics. Oliver and Boyd, Edinburgh, 248 pp. Mcllwraith. C. (1990) Osteochondralfragmentation of the distal aspect of the patella in horses. Equine vet. J. 22,157-163. Norrie. R.D. (1982) Fracture of the patella. In: Equine Medicine and Surgery. 3rd edn. American Veterinary Publications. Santa Barbara. pp 1139. Pankowski. R.L. and White. K.K. (1985) Fractures of the patella in horses. Comp. Conr. Educ. 7 , S566-S573. Parks. AH. and Wyn-Jones. G. (1988) Traumatic injuries of the patella in five horses. Equine vef J. 20.25-28. Stashak. T.S. (1987) Fracture of the patella. In: Adums'hmeness in Horses, 4th edn. Lea and Febiger. Philadelphia. pp 743. Trotter, G.W.. Mcllwraith. C.W. and Norrdin. R.W. (1983) A comparison of two surgical approaches to the equine femoropatellar joint for the treatment of osteochondritis dissecans. Vet. Surg. 12.33-40. Turner, A.S. (1984) Fractures of the patella. In: The Prucfice of' h r g e Animal Surgery. W.B. Saundea, Philadelphia. pp 866-867.
Receivedjiw pi~hlication:225.91 Accepted: 7.11.91
EQUINE VETERINARY JOURNAL
Equine vet. J . ( I 992) 24 (4) 264-268
Clinical and radiographic features, treatment and outcome in 15 horses with fracture of the medial aspect of the patella SUE DYSON, 1. WRIGHT, S. KOLD and N. VATISTAS Equine Clinical Unit, Animal Health Trust, Snailwell Road, Newmarket, Suffolk CB8 7DW, UK Summary
lateromedial view was also obtained in 6 horses.
A sagittal fracture of the medial aspect of the patella was Treatment identified in 15 horses, 2 of which had been kicked and 12 of which had hit a fixed fence while jumping. Eight horses showed One horse (No. 15) was humanely destroyed at the request of the concurrent fragmentation of the base of the patella, and 2 had owner. In Horse 14 the patellar fracture was initially repaired by sustained a concurrent fracture of the distal end of the lateral internal fixation, but the implant failed and the fracture fragment trochlear ridge of the femur. A cranioproximal-craniodistal was subsequently removed. Bone fragments in the distal aspect of oblique radiographic view was essential to identify the site of the the femoropatellar joint were removed from Horses 7 and 13, and a medial patellar fracture and to determine its configuration. non-displaced patellar fracture treated conservatively. However, the Fourteen horses were treated by surgical removal of the medial fracture fragment subsequently displaced and was ultimately patellar fracture fragment@). Of 12 horses (83%) without removed. The remaining horses (1-6, and 8-12) were treated by evidence of preexisting degenerative joint disease, 10 were surgical removal of the medial patellar fracture fragment(s). Fragmentation of the base of the patella was treated conservatively. treated successfully with return to full athletic function.
Introduction
Surgical techniquefor partial patellectomy
THERE are few reports in the literature concerning treatment of patellar fractures in the horse (Aldrete and Meagher 1981; Dik and Nemeth 1983; Colbern and Moore 1984; Pankowski and White 1985; Parks and Wyn-Jones 1988). Norrie (1982). Turner (1984) and Stashak (1987) suggested that articular fractures of the patella in horses carry a poor prognosis. In one series of 5 horses treated conservatively, only 2 recovered (Dik and Nemeth 1983), whereas a few case reports have indicated that prognosis may be improved by partial patellectomy (Colbern and Moore 1984; Pankowski and White 1985; Parks and Wyn-Jones 1988) or internal fixation (DeBowes, Grant, Chalman and Rantanen 1980 Aldrete and Meagher 1981). The purpose of this paper is to describe the history, clinical and radiographic features, treatment by partial patellectomy and outcome of 15 articular, sagittal fractures involving the medial aspect of the patella.
All horses were premedicated with im acepromazine (0.05 m@g bwt). Sedation was achieved with xylazine (I. 1 m a g bwt, iv) or detomidine (0.002 m a g bwt, iv), occasionally with the addition of butorphanol (0.001 m a g bwt, iv). Anaesthesia was induced with thiopentone (5 m a g bwt, iv) or ketamine (2.2 m a g bwt, iv), and maintained with a mixture of halothane in oxygen. Each horse was positioned in dorsal recumbency or in lateral recumbency with the affected limb lowermost. After preparing the site for aseptic surgery, a 15-25 cm curvilinear incision was made over the medial aspect of the femoropatellar joint, centred over the patella or the displaced fragment. The incision was continued through the subcutaneous tissues and the thick fascia associated with the insertions of the sartorius and gracilis muscles, into the femoropatellar joint. When possible the femoropatellar joint capsule was identified before being incised. The fracture fragment or fracture plane was identified by palpation, and the fragment was sharply dissected free from its soft tissue attachments. This involved the severance of a substantial or entire portion of the medial patellar and medial femoropatellar ligaments and part of the tendon of insertion of the vastus medialis. In more chronic cases, the fibrous tissue present between the fragment and parent bone was incised. In some cases the entire medial patellar cartilage was removed with the fracture fragment. A curette and/or rongeurs were used to debride and contour the parent bone. The trochlear ridges of the distal femur were examined for any concurrent damage or signs of degenerative joint disease. The joint was liberally flushed with either sterile saline and sodium penicillin, or a polyionic electrolyte solution (Hartmanns’ solution, Baxter Healthcare, Ltd., Compton, Newbury, Berks., UK). The joint capsule (when possible), the insertion of sartorius and gracilis, and the subcutaneous tissues were individually
Materials and methods An articular fracture of the medial aspect of the patella was diagnosed in 15 horses referred to the Equine Clinical Unit of the Animal Health Trust, between August 1984 and August 1990. The history of each horse was documented and a comprehensive clinical examination performed.
Radiographic examination Radiographic examination of the stifle was performed in the standing horse by using rare earth screens and orthochromatic G film (Kodak). All examinations included caudocranial, caudolateral-craniomedial oblique and cranioproximalcraniodistal oblique views (Butler et al 1992). A flexed
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TABLE 1: Descrlptlon, hlstory, radlographlc features, treatment and outcome of 15 horses with a patellar fracture Age Horse (years) Occupation
History (duration of lameness)
Radiographic features
Treatment
Outcome
Non-displaced comminuted fracture medial 1/4 of patella. Abnormal opacity of patella in LM view Displaced comminuted fracture medial 1/3 of patella. Abnormal opacity of patella in LM view. Degenerativejoint disease
Surgical removal of fracture fragments
Returned to full function: novice horse trials Lame (degenerative joint disease)
1
13
E
Kicked (8 weeks)
2
4
H
Kicked (19 weeks)
3
6
E
Lame in field (10 days)
4
7
E
5
7
E
Hit cross country fence (c24 h) Hit cross country fence (5 weeks)
6
8
E
Hit cross country fence (8 months)
7
8
E
Hit cross country fence (3 weeks)
7
E
10
E
Hit cross country fence (10 days) Hit cross country fence (4 days)
10
7
E
Hit cross country fence (11 days)
11
9
E
12
10
E
13
9
E
14
9
H
15
6
E
Lame associated with new bone formation at cranial aspect of fracture plane Surgical removal of Returned to full function: Slight fragmentation of base of Hit cross country fence patella. Slightly displaced fracture medial patellar fracture advanced horse trials of medial 1/6 of patella (c24 h) Non-displaced fracture medial 1/4 (i) Arthroscopic removal Returned to full function: Hit cross intermediate horse trials country fence of patella. Several small fragments of small fragments in distal aspect of femoropatellar (ii) Surgical removal of (9days) joint medial patellar fracturet (i) Internal fixation: Returned to full function: Displaced fracture medial 1/3 of Hit fence implants failed hunting jumping out of patella (ii) Surgical removal of field (2 weeks) medial patellar fracture Slight fragmentation of base of None Humanely destroyed Hit cross (owner's request) country fence patella. Displaced fracture of medial 1/4 of patella. Comminuted (c24 h) fracture of distal aspect of lateral trochlear ridge of femur Hit cross country fence (2 weeks)
Surgical removal of fracture fragments (confirmed preexisting degenerative joint disease) Surgical removal of medial patellar fracture (Tears noted in joint capsule) Surgical removal of medial patellar fracture Surgical removal of medial patellar fracture
Fragmentation of base of patella and small slightly displaced fracture of medial pole of patella Fragmentation of base of patella. Displaced fracture of medial 114 of patella Slight irregularity of outline of proximal aspect of patella. Displaced fracture of medial 116 of patella Fragmentation of base of patella. Surgical removal of medial patellar Displaced fracture medial 1/4 of patella. Degenerativejoint disease fracture (confirmed preexisting degenerative joint disease) Fragmentationof base of patella. (i) Arthroscopic removal of trochlear ridge Marginally displaced fracture of medial 1/4 of patella. Comminuted f ragments (ii) Surgical removal of fracture distal aspect of lateral medial patellar fracturet trochlear ridge of femur Surgical removal of Slight fragmentation of base of medial patellar fracture patella. Displaced fracture of medial 1/5 of patella Fragmentationof base of patella. Surgical removal of medial patellar fracture Dimlaced fracture of medial 1/4 and loose fragments of patella. Several fragments in distal aspect of femoropatellar joint Surgical removal of Displaced fracture medial 1/4 of patella. Several ill-defined medial patellar fracture opacities in distal aspect of femoropatellar joint Surgical removal of Slight fragmentation of base of patella. Displaced fracture medial medial patellar 1/5 of patella fracture
Returned to full function: novice horse trials Returned to full function: advanced horse trials Returned to full function: novice horse trials Lame (degenerativejoint disease)
Returned to full function: intermediate horse trials
Returnedto full function: intermediate horse trials Humanely destroyed (luxated patella in recovering from general anaesthesia) Returned to full function: intermediate horse trials
'E, eventing; H, hunting. +The initially non-displaced patellar fracture became displaced
closed with either three or five metric polyglactin 910 (Vicryl; Ethicon, Edinburgh, UK) or 3 metric polyglycolic acid (Dexon; Davies and Geck, Gosport, Hampshire, UK) in either a simple interrupted or simple continuous suture pattern. The skin was apposed with three metric monofilament nylon (Ethilon; Ethicon) in a vertical or horizontal mattress or simple interrupted suture
pattern, and a stent bandage was oversewn. Post-operative management
Sodium penicillin (iv, 3 times/day) or procaine penicillin (im, twice/day) (22,000 iuhcg bwt) was administered, starting at 30
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Table 2: Radlographlc features of 15 fractures of the medlal aspect of the patella Caudolateral-craniomedial oblique and lateromedial view No abnormality of patella Fragmentation of base of patella One or more large fragments proximal to patella Irregular opacity of patella Small fragments in distal aspect of femoropatellar joint Comminuted fracture of distal end of lateral trochlear ridge of femur
1
8 6' 2
3' 2
Cranioproximal-craniodistal oblique view Non-displaced simple articular fracture Displaced simple articular fracture Non-displaced comminuted articular fracture Displaced comminuted fracture
2t 11 1 1
'Unable to determine source of fragment(s).t2 non-displaced fractures which were treated conservatively initially, subsequently became displaced
Fig I : Cranioproximal-craniodisfoloblique view of a patella (Horse 12). There is a non-displaced fracture of its medial pole. The fracture fragment was removed, leaving the medial patellar cartilage intact
Fig 2: Cranioproximal-craniodistaloblique view of a patella (Horse 4 ) . There is a displacedfracture ofthe medial aspect ($the patella
Fig 4: Caudolateral-craniomedialoblique view of a stQle (Horse 7). There is a comminuted fracture c$ the distal aspect of the lateral rrochlear ridge. A fracture of the medial aspect of' the patella was not seen. but was confirmed on a CrPr-CrDiO view
History and clinical signs are summarised in Table I . Twelve of
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comminuted fracture of the distal end of the lateral trochlear ridge of the femur (Fig 4).Two horses (Nos 2 and 6) had evidence of degenerative joint disease. Perioperative complications
Horse 4 had considerable periarticular soft tissue swelling, despite treatment with non-steroidal anti-inflammatory drugs, when operated on 6 days after the onset of lameness. It recovered poorly from general anaesthesia, and there was considerable haemorrhage from the wound. The distal one-third of the incision subsequently dehisced, but healed by second intention with a good cosmetic outcome. Horse 9 had a catastrophic recovery from general anaesthesia: the patella luxated laterally and the horse was humanely destroyed. Post-mortem examination revealed evidence of pre-operative haemorrhage in the quadriceps muscles and subsequent avulsion of the patellar fibrocartilage and a fracture of the lateral proximal tibia. Horse 14, treated initially by internal fixation using 2 lag screws, made good progress until Day 20 after operation when severe lameness ensued. This was associated with displacement of the fracture and the distal screw and breakage of the proximal screw. The fracture fragment was subsequently removed successfully. Both horses (Nos 7 and 13) in which a nondisplaced patellar fracture was initially treated conservatively, following arthroscopic removal of small fracture fragments from the distal aspect of the femoropatellar joint, subsequently underwent a second surgical procedure to remove the medial patellar fracture fragment due to its displacement (Fig 5). Follow up
(W Fig 5: Cranioproximal-craniodistaloblique views of the patella of Horse 13: (a) 9 days and (b) 63 days ajier the onset of lameness. The nondisplaced fracture (a)subsequently displaced (b)
the 15 horses had hit a fixed fence, I I whilst in competition (horse trials). Although several of these horses completed the cross-country course, the majority pulled up lame shortly after hitting the fence. Some of the riders could not recall the horse hitting a fence but this was always subsequently verified by fence judges or spectators. Two horses had been kicked. Most horses would bear full weight on the limb but were inclined to stand with the heel elevated and the limb partly flexed. Distension of the femoropatellar joint capsule and a variable amount of localised periarticular soft tissue swelling usually developed within 24 h. Palpable or audible crepitus was a variable feature. Horses usually resented full flexion of the limb, but tolerated well the limb being held in the 'shoeing' position. The initial degree of lameness at the walk and the trot varied from moderate to severe, and persisted, albeit improving slightly over the following days. Radiographic examinations
In all horses a cranioproximal-craniodistaloblique (CrPr-CrDiO) view was essential to identify the site of a fracture of the patella and to confirm its configuration (Table 2) (Figs I and 2). In 8 horses there was slight fragmentation of the base of the patella (Fig 3) seen in a caudolateral-craniomedial oblique (CdL-CrMO) or lateromedial (LM) views (Table 2). One or more fragments of undetermined source were seen proximal to the patella in 6 horses in CdL-CrMO or LM views, and small fragments in the distal aspect of the femoropatellar joint were seen in 3 horses (Nos 9, 10 and 13). Two horses (Nos 7 and 15) had sustained a concurrent
One horse (No. 15) was humanely destroyed at the owner's request (Table I ) and a second horse (No. 9) was destroyed after complications during recovery from anaesthesia. l k o horses with pre-existing degenerative joint disease (Nos 2 and 6) which presented 10 weeks and 8 months respectively after onset of lameness were considerably improved but remained lame. Of the remaining I I horses, 10 have returned to full athletic function at the same or higher level than pre-operatively. None of these horses has experienced recurrent lameness related to the stifle in the period of follow-up (8 months to 7 years). Eight of these horses have been re-examined radiographically 3 months to 3 years post-operatively and none has shown evidence of modelling or fragmentation of the apex of the patella, or other secondary changes. Several horses showed mild hindlimb stiffness when work was first resumed but as work intensity increased and symmetrical hindlimb musculature was redeveloped, these minor gait abnormalities resolved. The cosmetic result was good in all cases.
Discussion The most common cause of patellar fractures is trauma (Hickman 1964; Aldrete and Meagher 1981; Colbern and Moore 1984; Pankowski and White 1985; Parks and Wyn-Jones 1988), usually as a result of a kick or hitting a jump. In the present series 12 of 15 horses hit a fixed obstacle while jumping. In this insfance the impact on the patella occurs when the stifle is partly flexed and the bone is fixed in the femoral trochlea (Pankowski and White 1985). Dik and Nemeth (1983) suggested that extreme muscle contractions may lead to avulsion of the medial patellar angle. However, no such history was recorded in the present series and other authors (Hickman 1964; Pankowski and White 1985) have suggested that intense contraction of the quadriceps group is more likely to cause a fracture orientated along soft tissue attachments or across the body of the patella. The experiencespf this series suggest that early radiographic
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examination is indicated in horses with known trauma to the stifle region after hitting a fixed fence. Even if abnormalities are detected in caudocranial, CdL-CrMO or LM views, a CrPr-CrDiO view should be included, since otherwise a patellar fracture may be missed. Evidence of degenerative joint disease appears to warrant a more guarded prognosis for return to athletic function. The results of this series indicate that apparently stable, nondisplaced fractures may become displaced, and since degenerative joint disease is a likely sequel to an articular fracture, surgical management is the treatment of choice, confirming the conclusions of Norrie ( I 982). Dik and Nemeth ( I 983), Turner (1984). Stashak (1987) and Auer (1991). Pre-operative appraisal should include a careful clinical examination and a close scrutiny of a complete set of radiographs. We failed to detect damage to the quadriceps muscles of Horse 9 pre-operatively. and the patella luxated laterally during recovery from anaesthesia. Based upon this case, and Horse 4 which had extensive periarticular soft tissue swelling pre-operatively and subsequently experienced partial wound dehiscence, we recommend that surgery should be delayed until the acute inflammatory response has subsided. The potential for primary failure of the surgical closure of the medial parapatellar incision must always be borne in mind. Concurrent fragmentation of the base of the patella was treated conservatively. Such fragmentation has been seen alone after hitting a fixed fence when jumping, and associated lameness has resolved following box rest and controlled walking exercise for 8-12 weeks (S. Dyson, unpublished data). The results of follow-up radiography indicate that in some cases the fragments disappear, presumably by healing the parent bone or resorption, whereas in others they persist for a long time unassociated with lameness. Aldrete and Meagher ( I98 I ) reported the successful repair of a simple sagittal fracture of the medial one-third of the patella by internal fixation. In contrast to Horse 14, 3 rather than 2 4.5-mm SIF cortical bone screws were inserted using the lag principle to stabilise the fragment. Aldrete and Meagher (198 I ) and Trotter, McIlwraith and Norrdin (1983) suggest that, after a stifle arthrotomy. horses should be cross-tied to prevent recumbency and the associated excessive wound tension developing due to flexion. Although cross-tying may have benefitted the case in the present material, the failure of the implants did not occur until almost 3 weeks after surgery. The use of 5.5-mm ASIF cortical screws may also have advantages in preventing breakage and dislocation of the implants. Partial patellectomy is a relatively straightforward surgical procedure, removing the problems of accurate fracture reduction, and screw placement, and possible implant failure. The results of this case series strongly support the encouraging case reports of Colbem and Moore (1984), Pankowski and White (1985) and Parks and Wyn-Jones (1988) and provide much longer follow-up data (8 months to 7 years) in a group of predominantly competition horses. In this series 10 of 12 horses (83%) without evidence of pre-existing degenerative joint disease were treated successfully with full return to athletic function, 2 of which have competed internationally. Concurrent fractures of the distal aspect of the lateral trochlear ridge did not appear to affect the outcome adversely. In the immediate post-operative period the horses were allowed to lie down and only one horse (No. 4) had secondary complications which were probably related to premature surgery
and further trauma sustained during recovery from anaesthesia. To minimise the risks of post-operative complications the surgical technique could be modified by examining the fracture arthroscopically, identifying it with needles and then making a small incision directly over the fragment. The surgical procedure involved transection of the medial patellar ligament and in most cases removal of the medial patellar cartilage. However. in this series no complications arose in contrast to the report of McIlwraith (1990) and Gibson, McIlwraith, Park and Norrdin (1989) following clinical or experimental medial patellar desmotomy. This may reflect the small number in the case series (although comparable to the report of Gibson el a/ (1989)). or altered biomechanical forces following removal of part of the patella per se. In conclusion, we strongly recommend treatment of medial patellar fractures by partial patellectomy but caution the reader to evaluate each horse carefully, both clinically and radiographically, to detect concurrent soft tissue or bony pathology which may adversely influence the outcome.
Acknowledgements We thank the referring veterinarians and the staff of the Equine Clinical Unit of the Animal Health Trust; and Jan Butler for preparing the illustrations. N. J. Vatistas is supported by a generous grant from the Marjorie Coote Animal Charity Trust.
References Aldrete. A.V. and Meagher. D.M. (1981) Lag screw fixation of a patellar fracture in a horse. Vef. Surg. 10. 143-148. Auer. J. (1991) In: Equine Medicine and Surgery. 4th edn. Vol 11. Eds: P. Colahan. J. Mayhew. A. Merritt. and 1. Moore. American Veterinary Publications. Santa Barbara. pp 1489-1491. Butler. J.. Colles. C.. Dyson. S.. Kold. S. and Poulos, P. (1992) Clinical Radiology of'fhe Horse. Blackwell Scientific Publications.Oxford. Colbem. G.T. and Moore, J.N. (1984) Surgical management of proximal articular fracture of the patella in a horse. J. Am. w f . med. Ass. 185,543-545. DeBowes. R.. Grant. B.. Chalman. J. and Rantanen. N. (1980) Fractured patella in a horse. Equine Pracfice 2.49-53. Dik, K.J. and Nemeth. F. (1983) Traumatic patellar fractures in the horse. Equine vet. J. 15.244-247. Gibson. K.. Mcllwraith. C., Park, R. and Norrdin, R. (1989) Production of patellar lesions by medial patellar desmotomy in normal horses. Vef. Surg. 18, 466-471. Hickman. J. (1964) V e f e r i w v Onhopuedics. Oliver and Boyd, Edinburgh, 248 pp. Mcllwraith. C. (1990) Osteochondralfragmentation of the distal aspect of the patella in horses. Equine vet. J. 22,157-163. Norrie. R.D. (1982) Fracture of the patella. In: Equine Medicine and Surgery. 3rd edn. American Veterinary Publications. Santa Barbara. pp 1139. Pankowski. R.L. and White. K.K. (1985) Fractures of the patella in horses. Comp. Conr. Educ. 7 , S566-S573. Parks. AH. and Wyn-Jones. G. (1988) Traumatic injuries of the patella in five horses. Equine vef J. 20.25-28. Stashak. T.S. (1987) Fracture of the patella. In: Adums'hmeness in Horses, 4th edn. Lea and Febiger. Philadelphia. pp 743. Trotter, G.W.. Mcllwraith. C.W. and Norrdin. R.W. (1983) A comparison of two surgical approaches to the equine femoropatellar joint for the treatment of osteochondritis dissecans. Vet. Surg. 12.33-40. Turner, A.S. (1984) Fractures of the patella. In: The Prucfice of' h r g e Animal Surgery. W.B. Saundea, Philadelphia. pp 866-867.
Receivedjiw pi~hlication:225.91 Accepted: 7.11.91
