Major Lower Extremity Lawnmower Injuries in Children

John P. Dormans, M.D. Michael Azzoni, M.D. Richard S. Davidson, M.D. Denis S. Drummond, M.D.


ABSTRACT

Between 1983 and 1993, 16 children with 18 lower extremity power lawnmower-related injuries were treated at Children's Hospital of Philadelphia. Eleven of 16 patients (69%), were by-standers or non-operators. The average age at injury was four years and nine months. Length of follow-up average 3.8 years. There was an average of 4.9 procedures per patient. Fourteen of the 18 limbs injured required eventual amputation (78%).

We propose a new classification of lawn mower injuries in children. One, a shredding type injury, was most common (16 of 18 limbs) and was either intercalary or distal. The second was a pauci-laceration type (two of 18 limbs). Of the four salvaged limbs, two were of shredding type and on most recent follow up are considered poor results. The two patients with the pauci-laceration type injuries and limb salvage are considered to have excellent results.

All patients with a shredding type of injury ultimately required amputation or had poor result with the salvaged limb. Limb salvage surgery was associated with prolonged hospitalizations, a higher incidence of surgical problems, a longer treatment course and more complications than early ablative procedures.

INTRODUCTION

Lawnmowers remain a common source of serious injury and morbidity for children. An estimated 75,000 lawnmower related injuries occur annually in the United States(l0). The estimated annual cost for these injuries is $253 million, not including monetary damage for pain and suffering (10). It is estimated that seven million new lawnmowers are purchased annually and that over thirty million are now used in the United States (7). Lawnmowing is a job often assigned to older children and teenagers. It is not surprising, therefore, that a large percentage of lawn mower injuries involve children (5,6,7,14). Lower extremity injuries, particularly involving the forefoot, are most common (4,13). According to the Consumer Product Safety Commission, children less than 14 years of age and adults over 44 years of age are at greatest risk of injury and children less than 6 years of age have the greatest risk of death resulting from lawn injuries (11).

Power lawnmowers are capable of generating tremendous force. A typical 26 inch rotary lawn mower blade rotating at 3,000 revolutions per minute develops a kinetic energy of 2100 pounds (12). Lawnmower injuries to children differ from comparable injuries to adults in several ways. First, the child's growth potential may be altered by direct injury to the physis, by indirect stimulation of growth by the repair process or by inhibition of growth by neurovascular injury to that part. Second, vessel size may influence the choice of free tissue transplants (5) or the ability to repair a vessel. Third, children in general tolerate prolonged immobilization better than adults and children tend to have better rehabilitative potential as compared with their adult counterparts.

MATERIALS AND METHODS

Since 1983, children were treated operatively at Children's Hospital of Philadelphia for lawnmower-related injuries. Of these, 16 children had extensive power lawnmower injuries of the lower extremities. The remaining patients had projectile injuries or injuries to parts other than the lower extremity injuries. Eighteen lower extremities were injured in these 16 patients. There were eleven boys and five girls. The average age at injury was four years and nine months with a range from 23 months to 9 years. (Table 1. ).

 

 

All patients were either admitted directly to Children's Hospital of Philadelphia or transferred following initial evaluation and stabilization at a community hospital. All arrived within eight hours of the injury. Patients were evaluated and immediately taken to surgery where the wounds were examined and debridement, irrigation and stabilization were performed. All patients were treated with fluid replacement, blood replacement (when appropriate) and intravenous triple antibiotics (penicillin, cephazolin and aminoglycoside). Tetanus status was evaluated and appropriate coverage used. Length of follow-up averaged 3.8 years (range 24 months to 10 years - Table 1. ). A cost analysis was performed on those patients with sufficient follow-up.

RESULTS

All sixteen patients were injured by power lawnmowers, (11 riding and 5 "push" lawnmowers). Eleven of sixteen patients were by-standers or non-operators. Three of these were being given a "ride" on a riding lawnmower when they fell and were run over by the mower. Five of the 16 were operators. One of these patients was injured as he attempted to move an object from the path of his moving lawnmower. Another patient slid under his lawnmower while mowing wet grass on an incline. Three other injuries occurred when a "push-type mower" was pulled over the operator's foot.Three injuries (19%) occurred in bad weather.

Open fractures and fracture dislocations occurred in each case. All of the injuries involved soft tissue injury. All wounds were left open initially and closure or plastics procedures delayed until the wounds were clean and the soft tissues proved viable. All patients had at least three formal debridement and irrigation procedures using pulsed lavage in all cases. The average hospitalization was 24 days. There were 78 operations performed for 16 patients, an average of 4.9 operations per patient (range three to 12 operations-Table 2. ).

 

Fourteen of 18 extremities eventually required ablative procedures (Table 3. ). Seven patients required below-knee amputations, one of which was subsequently revised to a knee disarticulation. Three patients required Syme's amputations. Two patients required transmetatarsal amputations and two required toe amputations.

In those not requiring early ablative procedures but with associate fractures and in those with intercalary injuries, rigid anatomic stabilization of fractures and fracture dislocations were achieved with external fixation devices in the majority of our patients. K wires and casts were used less frequently in selected instances.

Two types of lawn mower injuries were identified. One, a shredding type injury, was most common (16 of 18 limbs) and was either intercalary or distal. The second was a pauci-laceration type (two of the 18 limbs). Of the four salvaged limbs, two were of the shredding type and on most recent follow up are considered poor results. The two single laceration types are considered as excellent results.Both patients with shredding type of injuries who did not have amputations had intercalary, skiving type injuries with sparing of major neurovascular structures. One had major intra-articular and physeal injuries to the knee and subsequently required a knee arthrodesis which failed and has recently undergone "distraction osteogenesis" for lengthening and simultaneous compression knee arthrodesis using the Ilizarov (TM) system. His ankle is stiff and weak and his projected discrepancy is 15 cm. The patient and his parents refuse amputation. The second patient with an intercalary shredding type of injury of the leg and ankle had limb salvage with 12 total procedures. After 10 years of follow-up, the foot is small, painful, deformed and stiff. The parents refuse amputation. The two patients with pauci-laceration type injuries have done well. One patient had two lacerations to the medial tendons and the posterior tibial nerve. He has done quite well and has full sensation, normal strength and mild subtalar stiffness. His heel is small and he often uses padding to prevent his heel from sliding up and out of the shoe's heel cup. The other patient with a pauci-laceration type injury had a laceration to the lateral aspect of the forefoot with lacerations of the lateral plantar nerve, long flexor tendons to the fourth and fifth digits and had associated fourth and fifth metatarsal fractures. The patient is currently ambulating without pain or functional deformity. Wound closure was achieved with delayed primary closure only in eight (44%), split thickness skin graft only (STSG) in five (28%), free vascular flaps combined with STSG in two patients (11%), tissue expansion combined with rotation flap in one patient (6%) and STSG combined with a local gastrocnemius rotation flap in one patient (6%).

Complications were frequent (44%) and are listed in Table 3. . The number and severity of complications correlated directly with the severity of the injury and attempts at limb salvage surgery.

Function appeared to be satisfactory in 13 of 16 patients with sufficient follow-up. Most wounds have healed satisfactorily, but some have thin, hard, tight coverage from STSG or original soft tissue injury. All amputation patients were ambulating pain-free in prostheses at last follow-up. Two patients required stump revision for stump growth.The only factors that appeared to correlate with outcome were the severity of the initial injury and the presence or absence of injury to vital structures such as arteries, nerves, physeal plates, articular cartilage, etc. (i.e. shredding type injuries vs. single laceration type injuries).

A cost analysis was available for nine of the 16 patients. Cost for all hospitalizations, tests, surgeries and follow-up visits was calculated and converted to 1993 dollars. The cost per patient ranged from $9775 to $243,450 (average $61,492) for these seven patients. All had reached a satisfactory stable course with no immediate need for future surgery. Eight of nine patients currently wear prostheses and will continue to required prosthetic adjustments, repairs and replacements as they continued to grow.

Psychosocial problems affecting patients, family members or both occurred in all instances. The range of problems included guilt, depression and suicidal thoughts. Lawsuits resulted in four of eleven cases.

DISCUSSION

Power lawnmower injuries are infrequent, but remain a source of significant injury and morbidity in children. Injuries are complex, frequently require prolonged treatment and often result in significant disability (5, 6, 14).

These injuries are preventable (6, 8, 16). The majority of our patients (eleven out of 16) were injured as by-standers or non-operators. In eight of these, the operator was simply not aware of the presence of the child in the area. This high percentage of injuries to non-operators is similar to the experience of Love et. al., where 25 of 27 patients seen were non-operators (7). Ross, however, reported that 11 of their 18 patients were passengers who fell from their riding mower (14).

All the children in this series were young children with an average of four years and nine months. According to the Consumer Product Safety Commission, children less than 14 years of age and adults over 44 years of age are at greatest risk of injury and children less than six years of age have the greatest risk of death (11). We believe it is inappropriate for children under 14 to operate or be anywhere near power lawnmowers.

Based on an analysis of the mechanism of injury of the patients in our series and the mechanisms given in other series of lawnmower injuries in children (5, 6, 7, 14), the following recommendations will lessen the incidence and severity of injuries. First and foremost, children should be supervised and kept safely away from any operating power lawnmower. The majority of our patients (69%) were by-standers or non-operators and would not have been injured if they had not been in the area where the power mower was being operated. Secondly, children should never be allowed to ride riding lawnmovers, with or without an adult. Two of the patients in this series were being given "rides" on power riding lawnmowers and subsequently fell off and under the lawnmower.

Thirdly, power lawnmowers should not be operated in wet or inclement weather. Fourthly, safety design features such as automatic shutoff when a riding lawnmower seat is empty are encouraged. One patient was removing debris from the path of his riding lawnmower when the mower engaged and ran over his lower extremity. One of the single laceration type injury patients was inadvertently run over when his father backed over the child's leg. When the father felt the impact of the collision, he rose from the seat and the blade disengaged. The father felt that the automatic shut-off feature of the lawnmower was directly responsible for preventing more serious injury.

All patients required at least three formal debridement and irrigation procedures prior to wound closure. Three patients developed infection in spite of aggressive surgical debridement and irrigation. All wounds were left open initially and closure or plastic procedures delayed until the wounds were clean and the soft tissues proved viable. Soft tissue coverage was achieved in accordance with standard plastic surgical techniques (2, 5, 17). Plastic surgery consultation was helpful in planning closure and in those cases where skin grafting or flaps were utilized. Most patients achieved coverage with delayed primary closure or STSG only (81%). Free vascular flaps combined with STSG were used in two patients (11%) and tissue expansion with a rotation flap in one patient (6%).

Amputation was eventually required in 14 of 18 limbs in our series (78%). Love, in a review of 27 children with lawnmower injuries reported an amputation rate of 70% (19 of 27 patients)(7).

Russell et. al., devised a limb salvage index (LSI) based on a seven part predictive index of extremity injuries in deciding limb salvage versus amputation (15). The limb salvage index (LSI) was devised primarily from adult population, most of whom had various mechanisms of injuries other than lawnmower injuries. While we found LSI useful in quantifying the severity of the injury, we found that it did not take into account several aspects of these injuries that are unique to children (potential for future growth, less tendency for joint stiffness and potential for stump growth).

Transdiaphyseal amputation should be avoided if possible, to prevent stump overgrowth, unless more important priorities dictate (i.e. saving the knee). Stump overgrowth occurs in 8-17% of children with transdiaphyseal amputations (1). In our series stump overgrowth requiring revision surgery occurred in two patients (12.5%). We anticipate that this number may increase as these children continue to be followed. In adults, split thickness skin grafts often do poorly and durable soft tissue coverage is desirable (18). In this series of children, seven patients required split thickness skin grafting and only one required surgery due to skin breakdown. In most cases where split thickness skin grafting was required, the segment to be grafted was relatively small (less than five cm2 in four of six). Whenever possible, attempts at either delayed primary closure, coverage with small areas STSG or flap coverage were preferred to large areas of STSG. Free flaps or local rotation flaps were used for more extensive soft tissue loss over bone or joints.

As with adults, joint injury may lead to stiffness. In general, however, children tend to have fewer problems with joint stiffness than their adult counterparts(5). Significant joint contracture was seen in two patients in this series (patients 2 and 5). In both cases loss of motion was related to intraarticular injury and partial loss of articular cartilage.

We believe the best candidates for limb salvage following lawnmower injuries are pauci-laceration type distal injuries and selected cases of intercalary injuries with less severe destruction. Both patients in this series with shredding intercalary injuries and limb salvage had involvement of articular cartilage and physes which created their own unique treatment dilemmas.While aggressive attempts at salvage were employed in our series, all patients with shredding type injuries either ultimately required amputation or had poor results. Limb salvage attempts may be appropriate in a small percentage of carefully selected patients, but inappropriate attempts at limb salvage may contribute to long hospitalizations, a higher incidence of surgical complication, increased expense and pain as compared with early ablative procedures. Physeal injuries and potential for future growth need to be taken into consideration in deciding on amputation versus limb salvage surgery. With the advent of more biologic techniques of limb lengthening the potential for limb salvage type procedures and the potential for lengthening shorter, less functional stumps may improve (3).

The Division of Orthopaedic Surgery Children's Hospital of Philadelphia

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