Case Report : Ballistic trauma
A 45-year-old policeman who allegedly misfired a 0.38 caliber bullet from his service revolver, presented to our emergency 12 h after sustaining the injury to his left knee. According to the patient, he forgot to secure the weapon with his belt using a chain as is customary. While attempting to rise from his seat in the police van, the gun, which was tucked loosely in his belt, fell-off. Almost immediately, the weapon hit the floor and the weapon lock opened-up leading to misfiring of the gun as it tossed on the ground. The knee was in a flexed position while disembarking from the van and came in the way of the bullet with the entry wound located just inferior-medial to the knee joint. The bullet traveled three centimeters in the proximal tibia (The proximal tibia is the upper portion of the bone where it widens to help form the knee joint)., over the inferior-medial aspect of left knee, joint before lodging in the inter-condylar notch of the knee joint. Initial wound dressing was done at a local center, following which patient presented to our emergency with a locked knee.
Investigations : The position of the bullet was confirmed on plain antero-posterior and lateral radiographs. Since the retrieval of the intra-articular bullet was considered an emergent procedure, no other radiologic investigation was done. All other routine blood parameters were within normal limits.
Treatment : The patient underwent arthroscopy-assisted bullet retrieval from the knee joint, under general anesthesia and tourniquet control. Through the antero-lateral-inferior portal, a large hematoma was washed out, and a thorough diagnostic knee examination performed. There was a partial tear of the anterior cruciate ligament, and the bullet was found displaced in the lateral gutter, due to the fluid distention. The lateral femoral condyle cartilage showed focal damage and both menisci were found to be intact. The exact location and ideal direction of the portal on the lateral aspect of the knee was confirmed using a spinal needle. The third portal was created directly over the spinal needle with a 11 number surgical blade . A fine-toothed artery forceps was introduced into the joint from the third portal to hold the bullet. The skin incision was extended when the bullet was subcutaneous, and the bullet was extracted under arthroscopic guidance . The redundant soft tissue and
the frayed articular cartilage were debrided to achieve balanced margins. All the six compartments (medial and lateral compartment, supracondylar space and inter-condylar notch, medial and lateral gutters) were reinspected for any remaining foreign particles and charred tissue. Adequate joint debridement and lavage was done, with an additional extrarticular debridement of the entry wound, before closure and an ankle free static knee immobilizer was applied. The patient was started on third generation cephalosporin and aminoglycoside postoper- atively iv for 3 days and oral for 3 weeks.
Outcome and follow :up The postoperative radiograph revealed a hairline fracture of the tibial condyle that was obscured in the initial radiographs behind the bullet and was decided to be treated conservatively. The knee immobilization was continued for another 3 weeks given the undisplaced fracture. The patient then underwent a magnetic resonance imaging (MRI) of the knee to delineate better the injury pattern to the soft tissues. The MRI revealed marrow edema in the lateral femoral condyle and the proximal tibia around the tibial eminence. It also corroborated the intra-operative findings of articular cartilage injury to the lateral femoral condyle. On the basis of the MRI findings, the patient was advised to continue knee immobilization for another 2 weeks, and gradual physiotherapy and range of motion exercises were started. There was no evidence of any infection or significant history of catching in the knee. This case was managed conservatively, and he regained complete range of motion from 08 to 1308 at the end of 3 months. The patient has remained asymptomatic with no effusion or synovitis in the knee till the last follow-up of 2 years.
Discussion: Intra-articular bullet as a foreign body has been sparingly reported in the literature. Bullet injuries around the knee are usually caused by intention or as part of criminal punishment. Rarely, this may be caused by accidental injury. The mecha-nism of injury in this case report is unique as it was caused due to accidental firing of the bullet from an unlocked gun, which accidentally fell from its holster. Also, although late migration of bullets from thigh has been reported, early arthroscopic retrieval of a bullet from the knee has been rarely reported in literature. The common foreign bodies in the knee that have been described are pencil lead, plastic bottle caps, glass and metallic debris, etc. The main problem with any intra-articular foreign body is the risk of bacterial contamination that may lead to late onset infective arthritis. A retained bullet can further compound the problem due to the possibility of lead induced arthritis. According to Hurst, there are four main criteria for achieving ideal results with the removal of foreign bodies. These are early diagnosis, adequate debridement and lavage, immobili-zation as deemed necessary and restoration of function. Eliciting proper history and trying to understand the mechanism of injury is of prime importance. Keeping a high index of suspicion for the possibility of intra-articular migration of a foreign body may help in early start of management. The presence of an entry wound should always force the examiner to look for the location of the foreign body. The presence of the foreign body in the peri-articular region must prompt a regular follow-up as delayed migration of the bullets has been reported. The key to prevention of the sub-acute or late septic arthritis is adequate debridement and thorough lavage of the joint and it can be achieved satisfactorily through arthro- scopic-assisted technique. The most common causative organisms in military ballistic injuries are Clostridia and beta-hemolytic streptococci. The most effective antibiotic for these organisms has been penicillin but given the possibility of penicillin resistance, cephalosporin or erythro- mycin may be added. In view of risk of lead induced arthropathy and the bullet serving as a nidus for infection, retrieval of bullet should be executed, sooner than later. It is known that a metal object freely floating or lodged in the intra-articular space can cause late erosion of the vital structures inside the knee and may even lead to delayed arthritis of the knee. There is an even higher chance of an early lead toxicity induced by the bullet and disseminated in the systemic circulation by the free synovial fluid. The main advantages of an arthroscopic-assisted removal of the shell is the minimal operative trauma to the joint, small skin incision, preservation of the blood supply to the joint and the overlying soft tissue envelope, the possibility of examina-tion of the joint in detail, and shortened recovery and rehabilitation time. In the present case, the knee immobiliza- tion was, however, continued for a longer period because of the associated fracture of the tibial eminence. The patient was still able to achieve full painless range of motion at the end of 3 months. The ideal placement of the portal for extraction of the foreign body is of paramount importance and should be dictated by its location. Care should be taken in avoiding a far lateral portal to decrease the chances of encountering inferior- lateral-ascending geniculate vessels, leading to excessive amount of bleeding. A precise knowledge of anatomy and a thorough experience in carrying out arthroscopic procedures around the knee is mandatory before undertaking this procedure. In the present case, an undisplaced fracture would have been picked up accurately if a computerized tomography scan had been undertaken before the procedure. The bullet, in the preoperative plain radiographs came in way of the fracture and obscured delineation of the fracture line. An MRI of the knee was performed in the postoperative follow-up for delineation of the fracture and to assess any more associated intra-articular injuries. Since the fracture was undisplaced and did not carry any significant risk for displacement or an intra-articular step-off, it was decided to treat it conservatively with immobilization in a knee brace. This present case report suggests that an early arthro-scopic removal of bullet along with antibiotic cover can help achieve a satisfactory result with minimal long-term morbidity.